AMENDED AND RESTATED MORTGAGE LOAN REPURCHASE AGREEMENT

PURCHASER:        UBS REAL ESTATE SECURITIES INC.

ADDRESS:          1285 AVENUE OF THE AMERICAS
                  NEW YORK, NEW YORK 10019
                  ATTENTION:    GEORGE A. MANGIARACINA
                  TELEPHONE: (212) 713-3734
                  ATTENTION:  ROBERT CARPENTER
                  TELEPHONE: (212) 713-8749

SELLER:           AMERICAN HOME MORTGAGE INVESTMENT CORP.

ADDRESS:          520 BROADHOLLOW ROAD
                  MELVILLE, NEW YORK 11747
                  ATTENTION: STEPHEN A. HOZIE, CHIEF FINANCIAL OFFICER
                  TELEPHONE:  (516) 396-7700

SELLER:           AMERICAN HOME MORTGAGE ACCEPTANCE, INC.

ADDRESS:          520 BROADHOLLOW ROAD
                  MELVILLE, NEW YORK 11747
                  ATTENTION: STEPHEN A. HOZIE, CHIEF FINANCIAL OFFICER
                  TELEPHONE:  (516) 396-7700

SELLER:           AMERICAN HOME MORTGAGE HOLDINGS, INC.

ADDRESS:          520 BROADHOLLOW ROAD
                  MELVILLE, NEW YORK 11747
                  ATTENTION: STEPHEN A. HOZIE, CHIEF FINANCIAL OFFICER
                  TELEPHONE:  (516) 396-7700

SELLER:           AMERICAN HOME MORTGAGE CORP.

ADDRESS:          520 BROADHOLLOW ROAD
                  MELVILLE, NEW YORK 11747
                  ATTENTION: MICHAEL STRAUSS, PRESIDENT
                  TELEPHONE:  (516) 396-7700

SELLER:           COLUMBIA NATIONAL, INCORPORATED

ADDRESS:          520 BROADHOLLOW ROAD
                  MELVILLE, NEW YORK 11747
                  ATTENTION: MICHAEL STRAUSS, PRESIDENT
                  TELEPHONE:  (516) 396-7700
                  ATTENTION: STEPHEN A. HOZIE, CHIEF FINANCIAL OFFICER
                  TELEPHONE:  (516) 396-7700

<PAGE>

DATE OF AGREEMENT:      FEBRUARY 6, 2004


                                      -2-
<PAGE>

                              TABLE OF CONTENTS

                                                                            Page
                                                                            ---

SECTION 1.  DEFINITIONS ...................................................    2
SECTION 2.  PROCEEDS FOR PURCHASES OF MORTGAGE LOANS ......................   16
SECTION 3.  PROCEDURE FOR REPURCHASES OF MORTGAGE LOANS ...................   19
SECTION 4.  TERMS OF EACH TRANSACTION .....................................   21
SECTION 5.  CASH ACCOUNT ..................................................   21
SECTION 6.  SERVICING OF THE MORTGAGE LOANS ...............................   22
SECTION 7.  REMEDIES; MARGIN DEFICITS .....................................   24
SECTION 8.  TRANSFER OF MORTGAGE LOAN BY PURCHASER ........................   26
SECTION 9.  RECORD TITLE TO MORTGAGE LOANS; INTENT OF PARTIES;
             SECURITY INTEREST ............................................   27
SECTION 10. REPRESENTATIONS AND WARRANTIES ................................   27
SECTION 11. COVENANTS OF THE SELLERS ......................................   31
SECTION 12. PERIODIC DUE DILIGENCE ........................................   36
SECTION 13. THIRD PARTY SERVICING .........................................   36
SECTION 14. CONFIDENTIALITY ...............................................   37
SECTION 15. TERM ..........................................................   37
SECTION 16. EXCLUSIVE BENEFIT OF PARTIES; ASSIGNMENT ......................   37
SECTION 17. AMENDMENTS; WAIVERS; CUMULATIVE RIGHTS ........................   37
SECTION 18. EXECUTION IN COUNTERPARTS .....................................   37
SECTION 19. EFFECT OF INVALIDITY OF PROVISIONS ............................   37
SECTION 20. GOVERNING LAW .................................................   37
SECTION 21. NOTICES .......................................................   37
SECTION 22. ENTIRE AGREEMENT ..............................................   38
SECTION 23. COSTS OF ENFORCEMENT ..........................................   38
SECTION 24. PURCHASER'S APPOINTMENT AS ATTORNEY-IN-FACT ...................   38
SECTION 25. SUBMISSION TO JURISDICTION; WAIVERS ...........................   39
SECTION 26. CONSTRUCTION ..................................................   40
SECTION 27. EFFECT OF AMENDMENT AND RESTATEMENT ...........................   41


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SCHEDULES

Schedule 1  Representations and Warranties regarding Mortgage Loans

EXHIBITS

Exhibit A   Closing Loan Purchase Detail Fields

Exhibit B   Rewarehousing Loan Purchase Detail Fields

Exhibit C   Conversion Loan Purchase Detail Fields

Exhibit D   Withdrawal/Deposit Notice

Exhibit E   Cash Account Wire Instructions

Exhibit F   Cash Account Adjustment Notice

Exhibit G   [Intentionally Left Blank]

Exhibit H   Purchaser's Wire Instructions to Seller

Exhibit I   UCC-1 Financing Statement

Exhibit J   Seller's Delivery Instructions

Exhibit K   Seller's Release

Exhibit L   Seller's Wire Instructions

Exhibit M   Warehouse Lender's Release

Exhibit N   Authorized Signatures of Seller

Exhibit O   Warehouse Lender's Wire Instructions

Exhibit P   MBS Swap Funding Program Selection Notice

Exhibit Q   Request For Mortgage Loan Shipment

Exhibit R   MBS Swap Shipment Documents

Exhibit S   Form of Closing Instruction Letter Insert

Exhibit T   Seller's Underwriting Guidelines

Exhibit U   Form of Opinion

Exhibit V   UCC Filing Jurisdictions

Exhibit W   Form of Servicer Notice

Exhibit X   Form of Covenant Compliance Letter

Exhibit Y   Form of Request for Purchase


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<PAGE>


             AMENDED AND RESTATED MORTGAGE LOAN REPURCHASE AGREEMENT

            THIS AMENDED AND RESTATED MORTGAGE LOAN REPURCHASE AGREEMENT, dated
as of the date set forth on the cover page hereof (as amended, supplemented or
otherwise modified from time to time, "Agreement"), among UBS REAL ESTATE
SECURITIES INC. ("Purchaser" or "UBSRES") and the Sellers whose names are set
forth on the cover page hereof (each a "Seller" and, collectively, the
"Sellers").

                                    RECITALS

            WHEREAS, the Purchaser; American Home Mortgage Holdings, Inc.,
American Home Mortgage Corp. and Columbia National, Incorporated (in such
capacity, the "Original American Home Parties"); and the Custodian are parties
to the Mortgage Loan Repurchase Agreement, dated as of February 26, 1999 as
amended, supplemented or otherwise modified prior to the date hereof (the
"Original Repurchase Agreement");

            WHEREAS, pursuant to the Original Repurchase Agreement, one or more
of the Original American Home Parties may have, in its sole discretion, offered
to sell to Purchaser from time to time Mortgage Loans (as defined therein),
subject to the related Seller's obligation to repurchase such Mortgage Loans in
accordance with the terms therein and Purchaser, in its sole discretion, may
have agreed to purchase such Mortgage Loans from such Seller in accordance with
the terms and conditions set forth in the Original Repurchase Agreement;

            WHEREAS, the Original American Home Parties and the Purchaser desire
to amend and restate the Original Repurchase Agreement as provided herein; and

            NOW, THEREFORE, for good and valuable consideration, the receipt and
adequacy of which are hereby acknowledged, the parties hereto hereby agree that
the Original Repurchase Agreement be amended and restated in its entirety as
follows:

                              PRELIMINARY STATEMENT

            Each Seller is engaged among other pursuits, in the business of
originating, purchasing and selling Mortgage Loans. Purchaser is engaged in,
among other pursuits, the business of purchasing Mortgage Loans.

            Each Seller may, in its sole discretion, offer to sell to Purchaser
from time to time Mortgage Loans, subject to the related Seller's obligation to
repurchase such Mortgage Loans in accordance with the terms herein and
Purchaser, in its sole discretion, may agree to purchase such Mortgage Loans
from such Seller in accordance with the terms and conditions set forth in this
Agreement. It is contemplated by the parties hereto that the Mortgage Loans
subject to this Agreement, from time to time, will become the subject of
transactions in which Purchaser purchases such Mortgage Loans from the related
Seller on a servicing released basis. The related Seller subsequently will offer
to sell such Mortgage Loans to Purchaser on a servicing released

<PAGE>

basis, and Purchaser, pursuant to one of the UBSRES Purchase Programs, may elect
to purchase such Mortgage Loans from such Seller.

            The parties hereto hereby agree as follows:

            Section 1. Definitions.

            Capitalized terms used but not defined herein shall have the
meanings set forth in the Custodial Agreement. As used in this Agreement, the
following terms shall have the following meanings:

            "Act of Insolvency": With respect to any party and its Affiliates,
(i) the filing of a petition, commencing, or authorizing the commencement of any
case or proceeding under any bankruptcy, insolvency, reorganization,
liquidation, dissolution or similar law relating to the protection of creditors,
or suffering any such petition or proceeding to be commenced by another which is
consented to, not timely contested or results in entry of an order for relief;
(ii) the seeking the appointment of a receiver, trustee, custodian or similar
official for such party or an Affiliate or any substantial part of the property
of either; (iii) the appointment of a receiver, conservator, or manager for such
party or an Affiliate by any governmental agency or authority having the
jurisdiction to do so; (iv) the making or offering by such party or an Affiliate
of a composition with its creditors or a general assignment for the benefit of
creditors; (v) the admission by such party or an Affiliate of such party of its
inability to pay its debts or discharge its obligations as they become due or
mature; or (vi) that any governmental authority or agency or any person, agency
or entity acting or purporting to act under governmental authority shall have
taken any action to condemn, seize or appropriate, or to assume custody or
control of, all or any substantial part of the property of such party or of any
of its Affiliates, or shall have taken any action to displace the management of
such party or of any of its Affiliates or to curtail its authority in the
conduct of the business of such party or of any of its Affiliates.

            "Affiliate": With respect to any Person, any "affiliate" of such
Person, as such term is defined in the Bankruptcy Code.

            "Agency": The Government National Mortgage Association ("GNMA"), the
Federal National Mortgage Association ("FNMA"), and the Federal Home Loan
Mortgage Corporation ("FHLMC"), as applicable.

            "Agency Approvals": Shall have the meaning ascribed thereto in
Section 10(a)(xii) of this Agreement.

            "Agency Eligible Mortgage Loan": A mortgage loan that is in strict
compliance with the eligibility requirements for swap or purchase by the
designated Agency, under the applicable Agency Guide and/or applicable Agency
Program.

            "Agency Guide": The GNMA Mortgage-Backed Securities Guide; the
Fannie Mae Selling Guide and the Fannie Mae Servicing Guide; the Freddie Mac
Sellers' and Servicers' Guide; as applicable, in each case as such Agency Guide
may be amended from time to time.


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<PAGE>

            "Agency Program": The specific purchase program under the relevant
Agency Guide or as otherwise approved by the Agency.

            "Assignee": With respect to this Agreement and any Mortgage Loan,
any assignee of the Purchaser pursuant to a pledge or rehypothecation of the
Mortgage Loan.

            "Asset Value": With respect to each Mortgage Loan, the lesser of (a)
the Market Value of such Mortgage Loan less the related Discount or (b) the
outstanding principal balance of such Mortgage Loan less the Discount; provided,
that, the Asset Value shall be deemed to be zero with respect to each Mortgage
Loan (1) in respect of which there is a breach of a representation and warranty
set forth in Schedule 1 (assuming each representation and warranty is made as of
the date Asset Value is determined), (2) in respect of which there is a
delinquency in the payment of principal and/or interest which continues for a
period in excess of twenty nine (29) calendar days (without regard to any
applicable grace periods), (3) which has not been repurchased by the related
Seller by its Scheduled Repurchase Date, or (4) which has been released from the
possession of the Custodian under the Custodial Agreement to the related Seller
for a period in excess of ten (10) calendar days; provided that the Purchaser
may, in its sole and absolute discretion, assign a market value above zero with
respect to any Mortgage Loan that would otherwise be deemed to have an Asset
Value of zero.

            "Authorized Signatory": With respect to each Seller, an officer of
such Seller who is authorized and empowered to request a purchase of Mortgage
Loans by the Purchaser pursuant to a Request for Purchase, and is indicated on
the Authorized Signatories of such Seller attached hereto as Exhibit N.

            "Bankruptcy Code": The United States Bankruptcy Code of 1978, as
amended from time to time.

            "Business Day": Any day other than (a) a Saturday, Sunday or other
day on which banks located in the City of New York, New York are authorized or
obligated by law or executive order to be closed, or (b) any day on which UBSRES
is closed for business, provided that notice thereof shall have been given not
less than seven calendar days prior to such day.

            "Capital Lease Obligations": For any Person, all obligations of such
Person to pay rent or other amounts under a lease of (or other agreement
conveying the right to use) Property to the extent such obligations are required
to be classified and accounted for as a capital lease on a balance sheet of such
Person under GAAP, and, for purposes of this Agreement, the amount of such
obligations shall be the capitalized amount thereof, determined in accordance
with GAAP.

            "Cash Account": A separate cash account established and maintained
by the Sellers at UBSRES under the conditions set forth in Section 5.

            "Cash Account Adjustment": An adjustment to the Cash Account Balance
pursuant to a Cash Account Adjustment Notice.


                                       3
<PAGE>

            "Cash Account Adjustment Notice": A cash account adjustment notice,
in the form of Exhibit F; to be used by Purchaser to notify the Sellers of any
adjustments to the Cash Account Balance.

            "Cash Account Balance": As of any date, the net amount of funds in
the Cash Account on such date.

            "Cash Account Interest Accrual": The simple interest calculation
posted on the last Business Day of each month resulting from the product of each
Business Day's Cash Account Balance and the Cash Account Interest Rate.

            "Cash Account Interest Rate": With respect to each month, the
average opening federal funds rate for such month. For the Cash Account, the
opening federal funds rate on a Business Day shall be counted as the Cash
Account Interest Rate until the next Business Day.

            "Cash Account Wire Instructions": The wire instructions, set forth
in a letter in the form of Exhibit E, to be used for the payment of funds to the
Sellers.

            "Closing Instruction Letter": With respect to each Wet Mortgage Loan
which is being originated in part by the proceeds of a Closing Transaction, the
instruction letter of the related Seller with respect to such origination which
is acknowledged by the Escrow Agent.

            "Closing Instruction Letter Insert": A paragraph in the form of
Exhibit S hereto which shall be inserted into the Closing Instruction Letter.

            "Closing Loan Purchase Detail": A loan purchase detail, prepared by
the related Seller and delivered by such Seller to Purchaser via electronic
transmission containing all information specified on Exhibit A (as such
information may be amended from time to time by notice from Purchaser to such
Seller) in a form acceptable to Purchaser, regarding the characteristics of a
Mortgage Loan being offered for sale by such Seller to Purchaser under a Closing
Transaction.

            "Closing Transaction": Any sale of a Mortgage Loan by the related
Seller to Purchaser, structured as either a Wet Funding or a Dry Funding,
wherein Purchaser wires the Disbursement Amount in accordance with the Escrow
Agent Standing Wire Instructions subject to an obligation of such Seller to
repurchase such Mortgage Loan pursuant to this Agreement.

            "Code": The Internal Revenue Code of 1986, as amended from time to
time.

            "Collateral": Each of the following items or types of property,
whether now owned or hereafter acquired, now existing or hereafter created and
wherever located: the Mortgage Loans, all mortgage loan documents (including,
without limitation, all promissory notes, all servicing records, servicing
agreements and any other collateral pledged or otherwise relating to such
Mortgage Loans), together with all files, documents, instruments, surveys,
certificates, correspondence, appraisals, computer programs, computer storage
media, accounting records and other books and records relating thereto, all
mortgage guaranties and insurance (issued by governmental agencies or otherwise)
and any mortgage insurance certificate or other document evidencing such
mortgage guaranties or insurance relating to any Mortgage Loan, all


                                       4
<PAGE>

Servicing Rights relating to the Mortgage Loans, any servicing accounts
established pursuant to any Servicing Agreement and all amounts on deposit
therein, from time to time, all purchase agreements or other agreements or
contracts relating to, constituting, or otherwise governing, any or all of the
foregoing to the extent they relate to the Mortgage Loans including the right to
receive principal and interest payments with respect to the Mortgage Loans and
the right to enforce such payments, the Cash Account and all monies from time to
time on deposit in the Cash Account, the Custodial Account and all monies from
time to time on deposit in the Custodial Account, all "general intangibles",
"accounts", "chattel paper" and "investment property" as defined in the UCC
relating to or constituting any and all of the foregoing, and any and all
replacements, substitutions, distributions on or proceeds of any and all of the
foregoing.

            "Collateral Receipt": With respect to each Wet Mortgage Loan, the
receipt by Custodian on a Business Day of a Dry Submission Package or Conduit
Submission Package.

            "Collateral Receipt Adjustment": The process initiated by Collateral
Receipt wherein the Pass-Through Rate on a Wet Mortgage Loan is reduced,
effective from the date of Collateral Receipt through one calendar day prior to
the Repurchase Date.

            "Collateral Receipt Date": With respect to each Wet Mortgage Loan,
the Business Day on which a Collateral Receipt occurs.

            "Conduit Funding Program": A program pursuant to the terms of the
Custodial Agreement and the Conduit Amended and Restated Mortgage Loan Purchase
Agreement dated as of the date set forth on the cover sheet thereof, among the
Sellers and Purchaser as amended from time to time.

            "Conduit Submission Package": The documents required to be delivered
by a Seller to Custodian under the Conduit Funding Program.

            "Conversion Loan Purchase Detail": A loan purchase detail, prepared
by the related Seller and delivered by such Seller to Purchaser via electronic
transmission containing the information set forth on Exhibit C, in a form
acceptable to Purchaser, regarding the characteristics of a Mortgage Loan that
is subject to repurchase and that is subsequently offered to Purchaser under the
Conduit Funding Program.

            "Credit File": All papers and records of whatever kind or
description, whether developed or originated by the related Seller or others,
required to document or service the Mortgage Loan; provided however, that such
Mortgage Loan papers, documents and records shall not include any Mortgage Loan
papers, documents or records which are contained in the Dry Submission Package.

            "Custodial Account": A separate custodial account, established and
maintained by the Sellers under the conditions set forth in Section 6(b), for
the deposit by the Sellers of all collections in respect of a Mortgage Loan that
are payable to Purchaser as the owner of the Mortgage Loan.

            "Custodial Agreement": The Amended and Restated Mortgage Loan
Custodial Agreement, dated as of the date set forth on the cover sheet thereof,
among the Sellers, Purchaser


                                       5
<PAGE>

and custodian, as amended from time to time. Such Amended and Restated Mortgage
Loan Custodial Agreement governs Purchaser's Whole Loan Purchase Program and
Conduit Funding Program.

            "Custodial Fee": With respect to each Repurchase, a fee payable to
Purchaser by the related Seller in the amount set forth on the related Funding
Confirmation, and remitted to Purchaser on the related Repurchase Date as a
component of the related Repurchase Price .

            "Custodian": The custodian named in the Custodial Agreement, and its
permitted successors hereunder.

            "Defective Mortgage Loan": A Mortgage Loan that is not in compliance
with this Agreement and/or the Electronic Tracking Agreement, including but not
limited to a Mortgage Loan that is not in compliance with the representations
and warranties set forth on Schedule 1 hereto.

            "Desired Funding Date": The Business Day indicated by the related
Seller on the Closing Loan Purchase Detail, on which such Seller desires
Purchaser to purchase a Mortgage Loan via a Wet Funding or a Dry Funding or the
Business Day indicated by such Seller on the Rewarehousing Loan Purchase Detail,
on which such Seller desires Purchaser to purchase a Mortgage Loan via a Dry
Funding.

            "Disbursement Amount": With respect to a Mortgage Loan, the amount
set forth on the related Closing Loan Purchase Detail or Rewarehousing Loan
Purchase Detail as the "Disbursement Amount".

            "Discount": With respect to each Mortgage Loan, the amount,
determined by the Purchaser in its sole and absolute discretion, set forth on
the related Funding Confirmation as the "Discount."

            "Document File": The Credit File and the Dry Submission Package.

            "Dry Funding": Either (i) a Closing Transaction initiated by the
delivery by a Seller, via electronic transmission to Purchaser of a Closing Loan
Purchase Detail and the receipt by Custodian of a Dry Submission Package or (ii)
a Rewarehousing Transaction initiated by the delivery by such Seller, via
electronic transmission to Purchaser, of a Rewarehousing Loan Purchase Detail, a
Warehouse Lender's or such Seller's Release and the Custodian's receipt of a Dry
Submission Package.

            "Dry Mortgage Loan": A Mortgage Loan with respect to which (i)
Custodian has received a Dry Submission Package and (ii) no Repurchase has
occurred.

            "Dry Submission Package": The documents required to be delivered by
a Seller to Custodian pursuant to the Custodial Agreement.

            "Due Date": The day of the month on which the Monthly Payment is due
on the Mortgage Loan.


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<PAGE>

            "Electronic Agent": MERSCORP, INC., and its successors in interest.

            "Electronic Tracking Agreement": The Electronic Tracking Agreement,
dated as of the date hereof, among Participant, Sellers, MERSCORP, Inc. and
Mortgage Electronic Registration Systems, Inc.; provided that if no Mortgage
Loans are or will be MERS Designated Mortgage Loans, all references herein to
the Electronic Tracking Agreement shall be disregarded.

            "Escrow Agent": The agent appointed by the Title Insurance Company
to administer the closing of a Mortgage Loan.

            "Escrow Agent Standing Wire Instructions": The wire instructions of
the Escrow Agent set forth in the applicable Closing Loan Purchase Detail, from
the related Seller to Purchaser for use when Purchaser wires Disbursement
Amounts for Wet Fundings and Dry Fundings structured as Closing Transactions.

            "Event of Default": The occurrence of any of the following events:
(i) an Act of Insolvency with respect to the related Seller or its Parent
Company; (ii) any representation or warranty made by the related Seller
hereunder shall have been incorrect or untrue in any material respect when made
or when deemed to have been made; (iii) the related Seller shall fail to
perform, or shall admit to Purchaser its inability to, or its intention not to,
perform any of its obligations hereunder or under the Electronic Tracking
Agreement; (iv) an event or events shall have occurred resulting in the
effective absence of a "repo market" or comparable "lending market" for
financing debt obligations secured by mortgage loans or securities or an event
or events shall have occurred resulting in the Purchaser not being able to
finance any Mortgage Loans through the "repo market" or "lending market" with
traditional counterparties at rates which would have been reasonable prior to
the occurrence of such event or events; (v) an event or events shall have
occurred resulting in the effective absence of a "securities market" for
securities backed by mortgage loans or an event or events shall have occurred
resulting in the Purchaser not being able to sell securities backed by mortgage
loans at prices which would have been reasonable prior to such event or events;
(vi) there shall have occurred a material adverse change in the "repo market" or
comparable "lending market" or in the financial condition of the Purchaser which
effects (or can reasonably be expected to effect) materially and adversely the
ability of the Purchaser to fund its obligations under this Agreement; (vii) the
related Seller or any of such Seller's Affiliates shall be in default beyond any
applicable grace period under any note, indenture, loan agreement, guaranty,
swap agreement or any other contract to which it is a party; (viii) the related
Seller shall fail to comply with the requirements of any of Section 7(h),
Sections 11(a) through 11(c) (inclusive), Section 11(e), Section 11(h) through
Section 11(j) (inclusive), or Section 11(n); (ix)(a) the related Seller shall
fail to comply with the requirements of any of Section 11(k) through Section
11(m) (inclusive) or (b) the related Seller shall fail to comply with the
requirements of any other subsection in Section 11 (other than those
specifically enumerated in preceding clauses (viii) or (ix)(a)), and such
default shall continue unremedied for a period of three Business Days; (x) if
the Purchaser has purchased MERS Designated Mortgage Loans, the Electronic
Tracking Agreement has for whatever reason been terminated or ceases to be in
full force and effect and the Purchaser (or the Custodian as its designee) shall
not have received an assignment of mortgage with respect to each MERS Designated
Mortgage Loan, in blank, in recordable form, but unrecorded; (xi) any materially
adverse change in the Property,


                                       7
<PAGE>

business, financial condition or prospects of the related Seller or any of its
Affiliates shall occur, in each case as determined by the Purchaser in its sole
discretion, or any other condition shall exist which, in the Purchaser's sole
discretion, constitutes a material impairment of such Seller's ability to
perform its obligations under this Agreement or any other document in connection
herewith; (xii) the discovery by the Purchaser of a condition or event which
existed at or prior to the execution hereof and which the Purchaser, in its sole
discretion, determines materially and adversely affects: (a) the condition
(financial or otherwise) of the related Seller, its Subsidiaries or Affiliates;
or (b) the ability of either the related Seller or Purchaser to fulfill its
respective obligations under this Agreement; or (xiii) the failure of any REIT
Seller to at any time continue to be (x) qualified as a real estate investment
trust as defined in Section 856 of the Code and (y) entitled to a dividend paid
deduction under Section 857 of the Code with respect to dividends paid by it
with respect to each taxable year for which it claims a deduction on its Form
1120 - REIT filed with the United States Internal Revenue Service for such year,
or the entering into by any REIT Seller of any material "prohibited
transactions" as defined in Sections 857(b) and 856(c) of the Code.

            "FDIC": The Federal Deposit Insurance Corporation or any successor
thereto.

            "Freddie Mac": Freddie Mac or any successor thereto.

            "Fannie Mae": Fannie Mae or any successor thereto.

            "Funding Confirmation": With respect to each Mortgage Loan purchased
by Purchaser from the related Seller via a single wire funds transaction on a
particular Business Day, the trade confirmation from Purchaser to such Seller
confirming such Seller's obligation to repurchase such Mortgage Loan from
Purchaser by the Scheduled Repurchase Date.

            "GAAP": Generally accepted accounting principles as in effect from
time to time in the United States.

            "GMNA": The Government National Mortgage Association or any
successor thereto.

            "Guarantee": As to any Person, any obligation of such Person
directly or indirectly guaranteeing any Indebtedness of any other Person or in
any manner providing for the payment of any Indebtedness of any other Person or
otherwise protecting the holder of such Indebtedness against loss (whether by
virtue of partnership arrangements, by agreement to keep-well, to purchase
assets, goods, securities or services, or to take-or-pay or otherwise); provided
that the term "Guarantee" shall not include (i) endorsements for collection or
deposit in the ordinary course of business, or (ii) obligations to make
servicing advances for delinquent taxes and insurance or other obligations in
respect of a Mortgaged Property, to the extent required by the Purchaser. The
amount of any Guarantee of a Person shall be deemed to be an amount equal to the
stated or determinable amount of the primary obligation in respect of which such
Guarantee is made or, if not stated or determinable, the maximum reasonably
anticipated liability in respect thereof as determined by such Person in good
faith. The terms "Guarantee" and "Guaranteed" used as verbs shall have
correlative meanings.


                                       8
<PAGE>

            "Incremental Pass-Through Rate": The amount by which the
Pass-Through Rate increases upon the occurrence of any event giving Purchaser
the right to elect a remedy pursuant to Section 7, which amount shall be set
forth in the applicable Funding Confirmation as the "Incremental Pass-Through
Rate".

            "Indebtedness": For any Person: (a) obligations created, issued or
incurred by such Person for borrowed money (whether by loan, the issuance and
sale of debt securities or the sale of Property to another Person subject to an
understanding or agreement, contingent or otherwise, to repurchase such Property
from such Person); (b) obligations of such Person to pay the deferred purchase
or acquisition price of Property or services, other than trade accounts payable
(other than for borrowed money) arising, and accrued expenses incurred, in the
ordinary course of business so long as such trade accounts payable are payable
within 90 days of the date the respective goods are delivered or the respective
services are rendered; (c) Indebtedness of others secured by a Lien on the
Property of such Person, whether or not the respective Indebtedness so secured
has been assumed by such Person; (d) obligations (contingent or otherwise) of
such Person in respect of letters of credit or similar instruments issued or
accepted by banks and other financial institutions for account of such Person;
(e) Capital Lease Obligations of such Person; (f) obligations of such Person
under repurchase agreements, sale/buy back agreements or like arrangements; (g)
Indebtedness of others Guaranteed by such Person; (h) all obligations of such
Person incurred in connection with the acquisition or carrying of fixed assets
by such Person; and (i) Indebtedness of general partnerships of which such
Person is a general partner.

            "Interest Rate Protection Agreement": With respect to any or all of
the Mortgage Loans, any short sale of US Treasury securities, or futures
contracts, or options related contracts, or interest rate swap, cap or collar
agreement or similar arrangement providing for protection against fluctuations
in interest rates or the exchange of nominal interest obligations either
generally or under specific contingencies and acceptable to Purchaser.

            "Interim Funder": With respect to each MERS Designated Mortgage
Loan, the Person named on the MERS(R)System as the interim funder pursuant to
the MERS Procedures Manual.

            "Investor": With respect to each MERS Designated Mortgage Loan, the
Person named on the MERS(R) System as the investor pursuant to the MERS
Procedures Manual.

            "Lien": Any mortgage, lien, pledge, charge, security interest or
similar encumbrance.

            "Losses": Any and all losses, claims, damages, liabilities or
expenses (including reasonable attorneys' fees) incurred by any person
specified; provided, however, that "Losses" shall not include any losses,
claims, damages, liabilities or expenses which would have been avoided had such
person taken reasonable actions to mitigate such losses, claims, damages,
liabilities or expenses.

            "Market Value": As of any date in respect of a Mortgage Loan, the
price at which such Mortgage Loan could readily be sold as determined by
Purchaser in its sole discretion,


                                       9
<PAGE>

which price may be determined to be zero. Purchaser's good faith determination
of Market Value shall be conclusive upon the parties.

            "MBS Swap Custodial Agreement": The custodial agreement, dated as of
the date set forth on the cover sheet thereof, among the Sellers, Purchaser and
custodian as amended from time to time. Such custodial agreement governs
Purchaser's MBS Swap Funding Program.

            "MBS Swap Funding Program": A program pursuant to the terms of (i)
the MBS Swap Mortgage Loan Participation Agreement dated as of the date set
forth on the cover sheet thereof, among the Sellers and Purchaser as amended
from time to time and (ii) the MBS Swap Custodial Agreement.

            "MBS Swap Funding Program Selection Notice": A notification that
identifies Mortgage Loans intended for the MBS Swap Funding Program provided by
the related Seller to Purchaser either (i) on the Closing Loan Purchase Detail
or Rewarehousing Loan Purchase Detail via the "MBS Swap Funding Program
Designation" field or (ii) via a facsimile transmission in the form of Exhibit
P, received by Purchaser prior to the Scheduled Repurchase Date, for any
Mortgage Loans previously purchased without the "MBS Swap Funding Program
Designation".

            "MBS Swap Shipment Documents": With respect to each Mortgage Loan
for which an MBS Swap Funding Program Selection Notice has been provided, the
documents required, as listed in Exhibit R, to be received by Purchaser from the
related Seller via facsimile transmission, prior to Purchaser's carrying out
such Seller's instructions for the Request for Mortgage Loan Shipment.

            "MBS Swap Submission Package": The documents required to be provided
by the related Seller to Purchaser with respect to each purchase under the MBS
Swap Funding Program, as described in the MBS Swap Mortgage Loan Participation
Agreement and MBS Swap Custodial Agreement.

            "MERS Designated Mortgage Loan": Mortgage Loans for which (a) the
related Seller has designated or will designate MERS as, and has taken or will
take such action as is necessary to cause MERS to be, the mortgagee of record,
as nominee for such Seller, in accordance with MERS Procedure Manual and (b) the
related Seller has designated or will designate the Purchaser as the Investor
and Interim Funder on the MERS(R)System.

            "MERS Procedure Manual": The MERS Procedures Manual attached as
Exhibit B to the Electronic Tracking Agreement, as it may be amended,
supplemented or otherwise modified from time to time.

            "MERS Report": The schedule listing MERS Designated Mortgage Loans
and other information prepared by the Electronic Agent pursuant to the
Electronic Tracking Agreement.

            "MERS(R)System": The Electronic Agent's mortgage electronic registry
system, as more particularly described in the MERS Procedures Manual.


                                       10
<PAGE>

            "Monthly Payment": The scheduled monthly payment of principal and
interest on a Mortgage Loan.

            "Moody's": Moody's Investors Service, Inc.

            "Mortgage": The mortgage, deed of trust or other instrument creating
a lien on an estate in fee simple in real property securing a Mortgage Note.

            "Mortgage Loan": A one-to-four family residential loan secured by a
Mortgage that is underwritten in accordance with the Underwriting Guidelines and
is subject to this Agreement.

            "Mortgage Note": The note or other evidence of the indebtedness of a
Mortgagor or secured by a Mortgage.

            "Mortgaged Property": The property subject to the lien of the
Mortgage securing a Mortgage Note.

            "Mortgagor": The obligor on a Mortgage Note.

            "NCUA": The National Credit Union Administration, or any successor
thereto.

            "Net Income": With respect to any Seller, for any period, the net
income of such Seller for such period as determined in accordance with GAAP.

            "Note Rate": The rate of interest borne by a Mortgage Note.

            "Original American Home Parties": Shall have the meaning assigned to
such term in the recitals hereof.

            "Original Repurchase Agreement": Shall have the meaning assigned to
such term in the recitals hereof.

            "OTS": The Office of Thrift Supervision, or any successor thereto.

            "Parent Company": A corporation or other entity owning, directly or
indirectly, more than 50% of the outstanding shares of voting stock of American
Home Mortgage Investment Corp., American Home Mortgage Acceptance, Inc.,
American Home Mortgage Holdings, Inc., American Home Mortgage Corp. and/or
Columbia National, Incorporated.

            "Pass-Through Rate": With respect to each Mortgage Loan, the rate at
which interest is passed through to Purchaser which initially shall be the rate
of interest specified on a Funding Confirmation as the "Pass-Through Rate".

            "Person": Any individual, corporation, company, voluntary
association, partnership, joint venture, limited liability company, trust,
unincorporated association or government (or any agency, instrumentality or
political subdivision thereof).


                                       11
<PAGE>

            "Property": Any right or interest in or to property of any kind
whatsoever, whether real, personal or mixed and whether tangible or intangible.

            "Purchase Date": With respect to a Mortgage Loan, the date on which
Purchaser purchases such Mortgage Loan from the related Seller.

            "Purchase Price": With respect to each Mortgage Loan, an amount
equal to the face amount of the Mortgage Loan less the Discount.

            "Purchaser": UBS Real Estate Securities Inc. and its successors.

            "Purchaser's Wire Instructions": The wire instructions, set forth in
a notice delivered by Purchaser to the related Seller in the form of Exhibit H,
containing the information to be used for the payment of all amounts due and
payable to Purchaser hereunder.

            "REIT Seller": As the case may be, American Home Mortgage Investment
Corp. and American Home Mortgage Acceptance, Inc.

            "REIT Status": With respect to any Person, such Person's status as a
real estate investment trust, as defined in Section 856(a) of the Code, that
satisfies the conditions and limitations set forth in Section 856(b) and 856(c)
of the Code.

            "Repurchase": With respect to any Mortgage Loan, the transaction by
which the related Seller remits the Repurchase Price to Purchaser and
simultaneously Purchaser purchases the Mortgage Loan with a netting of funds
resulting, governed by the terms of the applicable UBSRES Purchase Program.

            "Repurchase Date": With respect to any Mortgage Loan, the date that
the related Seller remits the Repurchase Price to Purchaser.

            "Repurchase Price": With respect to each Mortgage Loan, an amount
equal to the Purchase Price plus the Custodial Fee plus the product of the
Purchase Price of the Mortgage Loan, the Pass-Through Rate and the number of
calendar days from the Purchase Date to the Repurchase Date divided by 360.

            "Request for Mortgage Loan Shipment": Notification provided by the
related Seller to Purchaser via facsimile transmission in the form of Exhibit Q,
which presents Mortgage Loans to be delivered by Purchaser to the custodian as
set forth on the cover page of the MBS Swap Funding Program Custodial Agreement
or under the appropriate circumstances, Freddie Mac.

            "RESPA": Real Estate Settlement Procedures Act, as amended from time
to time.

            "Rewarehousing Loan Purchase Detail": A loan purchase detail,
prepared and submitted by the related Seller to Purchaser via electronic
transmission containing the information specified on Exhibit B (as such
information may be amended from time to time by notice from Purchaser to such
Seller) in a form acceptable to Purchaser, regarding the


                                       12
<PAGE>

characteristics of a Mortgage Loan being offered for sale by, such Seller to
Purchaser under a Rewarehousing Transaction.

            "Rewarehousing Transaction": Any sale of a Mortgage Loan by the
related Seller to Purchaser structured as a Dry Funding wherein Purchaser wires
the Disbursement Amount pursuant to the Warehouse Lender's Wire Instructions or
such Seller's Wire Instructions, as applicable, subject to an obligation of such
Seller to repurchase such Mortgage Loan pursuant to this Agreement.

            "RTC": The Resolution Trust Corporation or any successor thereto.

            "S&P": Standard and Poor's Ratings Services, a division of
McGraw-Hill Companies.

            "Scheduled Collateral Receipt Date": With respect to each Wet
Mortgage Loan, the Business Day, as set forth on the Funding Confirmation as the
"Collateral Receipt Date", by which a Collateral Receipt is required to occur,
such date to be within five (5) Business Days of a Wet Funding structured as a
Closing Transaction.

            "Scheduled Repurchase Date": With respect to each Mortgage Loan, the
Business Day as set forth on the Funding Confirmation as the "Repurchase Date",
by which a repurchase is required to occur, such date to be within five (5)
Business Days after the Purchase Date with respect to a Wet Mortgage Loan unless
such Mortgage Loan has become a Dry Mortgage Loan prior to such fifth Business
Day, (ii) within five (5) Business Days after the Collateral Receipt Date with
respect to a Dry Mortgage Loan or (iii) within five (5) Business Days after the
Purchase Date with respect to a Dry Mortgage Loan for which the related Seller
has provided Purchaser with an MBS Swap Funding Program Selection Notice,
unless, in any case, such date has been accelerated in connection with either an
Event of Default pursuant to Section 7(a), a Defective Mortgage Loan pursuant to
Section 7(b) or a Margin Deficit pursuant to Section 7(h).

            "Seller": Each Seller whose name is set forth on the cover page
hereof, and its permitted successors and assigns.

            "Seller's Delivery Instructions": With respect to each Mortgage Loan
for which the related Seller has remitted the Repurchase Price to Purchaser and
which Purchaser concurrently does not elect to purchase under a UBSRES Purchase
Program, the notification provided by such Seller to Purchaser via facsimile
transmission in the Form of Exhibit J, instructing Purchaser to deliver the Dry
Submission Package for such Mortgage Loan to the indicated address.

            "Seller's Release": A letter in the form of Exhibit K, delivered by
a when no Warehouse Lender has an interest in a Mortgage Loan, conditionally
releasing all of such Seller's interest in a Mortgage Loan upon receipt of
payment by such Seller.

            "Seller's Wire Instructions": The wire instructions set forth in a
letter in the form of Exhibit L, to be used for the payment of funds to the
related Seller when no Warehouse Lender has an interest in the Mortgage Loans to
which such payment relates.


                                       13
<PAGE>

            "Sellers": The Sellers whose names are set forth on the cover page
hereof, and their permitted successors and assigns.

            "Servicer": Shall have the meaning provided in Section 13 hereof.

            "Servicing Agreement": Shall have the meaning provided in Section 13
hereof.

            "Servicing Rights": Any and all of the following: (a) any and all
rights to service the Mortgage Loans; (b) any payments to or monies received by
a Seller or any other Person for servicing the Mortgage Loans; (c) any late
fees, penalties or similar payments with respect to the Mortgage Loans; (d) all
agreements or documents creating, defining or evidencing any such servicing
rights to the extent they relate to such servicing rights and all rights of the
related Seller or any other Person thereunder; (e) escrow payments or other
similar payments with respect to the Mortgage Loans and any amounts actually
collected by a Seller or any other Person with respect thereto; and (f) all
accounts and other rights to payment related to the Mortgage Loans.

            "Submission Package": A Conduit Submission Package, a Dry Submission
Package or a MBS Swap Submission Package, as applicable.

            "Subsidiary": With respect to any Person, any corporation,
partnership or other entity of which at least a majority of the securities or
other ownership interests having by the terms thereof ordinary voting power to
elect a majority of the board of directors or other persons performing similar
functions of such corporation, partnership or other entity (irrespective of
whether or not at the time securities or other ownership interests of any other
class or classes of such corporation, partnership or other entity shall have or
might have voting power by reason of the happening of any contingency) is at the
time directly or indirectly owned or controlled by such Person or one or more
Subsidiaries of such Person or by such Person and one or more Subsidiaries of
such Person.

            "Successor Servicer": An entity designated by Purchaser, in
conformity with Section 7, to replace the related Seller as servicer for
Purchaser.

            "Supplemental Amount": With respect to each Mortgage Loan, an amount
equal to the Disbursement Amount less the Purchase Price.

            "Tangible Net Worth": With respect to any Seller, as of a particular
date,

                  (i) all amounts which would be included under capital on a
            balance sheet of such Seller at such date, determined in accordance
            with GAAP, less

                  (ii) amounts owing to such Seller from Affiliates, and

                  (iii) intangible assets.

            "Title Insurance Company": A title insurance company acceptable to
Purchaser in its sole discretion.


                                       14
<PAGE>

            "Total Indebtedness": With respect to any Seller, for any period,
the aggregate Indebtedness of such Seller during such period less the amount of
any nonspecific balance sheet reserves maintained in accordance with GAAP.

            "Transaction": Any sale of a Mortgage Loan by the related Seller to
Purchaser subject to an obligation of such Seller to repurchase such Mortgage
Loan pursuant to a Funding Confirmation in accordance with this Agreement.

            "UBSRES Purchase Program": Purchaser's Conduit Funding Program or
MBS Swap Funding Program as applicable.

            "UCC": The Uniform Commercial Code, as enacted in each applicable
state.

            "Underwriting Guidelines": The underwriting guidelines delivered by
the related Seller to Purchaser on or prior to the date hereof and as may be
supplemented from time to time thereafter, a copy of which is attached hereto as
Exhibit T.

            "Warehouse Lender ": Any lender providing financing to the related
Seller in any fractional amount for the purpose of originating or purchasing
Mortgage Loans, which lender has a security interest in such Mortgage Loans as
collateral for the obligations of such Seller to such lender.

            "Warehouse Lender's Release": A letter in the form of Exhibit M from
a Warehouse Lender to Purchaser, conditionally releasing all of Warehouse
Lender's right, title and interest in certain Mortgage Loans identified therein
upon receipt of payment by Warehouse Lender.

            "Warehouse Lender's Wire Instructions": The wire instructions set
forth in a letter in the form of Exhibit O, from a Warehouse Lender who has an
interest in the Mortgage Loans to which such payment relates.

            "Wet Funding": A Closing Transaction initiated by the delivery by a
Seller, either via electronic or facsimile transmission to Purchaser, of a
Closing Loan Purchase Detail and a pledge by such Seller to Purchaser to deliver
to Custodian a Dry Submission Package or Conduit Submission Package by the
Scheduled Collateral Receipt Date.

            "Wet Mortgage Loan": A Mortgage Loan for which Custodian on behalf
of Purchaser, does not have physical possession of the related complete Dry
Submission Package and which the related Seller has agreed to pledge to
Purchaser all right, title and interest in, to and under such Mortgage Loan,
free and clear of all liens, pledges, charges, encumbrances or security
interests of any nature.

            "Whole Loan Purchase Program": A program pursuant to the terms of
the Custodial Agreement and this Agreement.

            "Withdrawal/Deposit Notice": A notice, substantially in the form of
Exhibit D, delivered by the Sellers to Purchaser, from time to time, in
connection with withdrawals from and deposits to the Cash Account.


                                       15
<PAGE>

            "Wire Fee": For each disbursement relating to a Closing Transaction,
a fee payable to Purchaser by the related Seller as set forth in the Funding
Confirmation.

            Section 2. Proceeds for Purchases of Mortgage Loans.

            (a) General Procedures for Purchases of Mortgage Loans.

                        (1) Pursuant to either a Wet Funding or a Dry Funding,
                  Purchaser may, in its sole discretion, from time to time,
                  purchase one or more Mortgage Loans from the related Seller on
                  a "servicing released" basis subject to an obligation of such
                  Seller to repurchase such Mortgage Loans and subsequently to
                  offer to sell such Mortgage Loans to Purchaser pursuant to one
                  of the UBSRES Purchase Programs. Such Seller shall be deemed
                  to make, and hereby makes, for the benefit of Purchaser, as of
                  the applicable dates specified in Section 10, the
                  representations and warranties set forth on Schedule 1 hereto
                  in respect of each such Mortgage Loan.

                        (2) Notwithstanding the satisfaction by the related
                  Seller of the conditions specified in this Section, this is
                  not a committed facility, Purchaser is not obligated to
                  purchase any Mortgage Loan offered to it hereunder and the
                  decision of Purchaser to purchase such Mortgage Loan shall be
                  at Purchaser's sole discretion. In the event that Purchaser
                  elects to reject a Mortgage Loan offered by such Seller for
                  purchase by Purchaser in a Wet Funding or a Dry Funding for
                  any reason and/or does not transmit the Disbursement Amount,
                  any Dry Submission Package delivered to Custodian in
                  anticipation of such purchase shall be returned by Custodian
                  in accordance with the terms of the Custodial Agreement.

            (b) Specific Procedures for Purchases of Mortgage Loans related to
Wet Fundings.

                        (1) Prior to Purchaser's election to purchase any
                  Mortgage Loan pursuant to a Wet Funding, Purchaser shall have
                  received from the related Seller (i) a Closing Loan Purchase
                  Detail in electronic format and (ii) a Request to Purchase, in
                  the form attached hereto as Exhibit Y, signed by an Authorized
                  Signatory of such Seller, and (iii) evidence that the Cash
                  Account Balance is not less than the sum of the Supplemental
                  Amount plus the Wire Fee. The terms and conditions of each
                  such purchase shall be set forth in this Agreement and in the
                  applicable Funding Confirmation.

                        (2) If Purchaser elects to purchase any Mortgage Loan
                  pursuant to a Wet Funding, Purchaser shall (i) withdraw the
                  Supplemental Amount, if any, and the Wire Fee from the Cash
                  Account and (ii) pay the Disbursement Amount for such Mortgage
                  Loans to the Escrow Agent by wire transfer of immediately
                  available funds in accordance with the Escrow Agent Standing
                  Wire Instructions.


                                       16
<PAGE>

                        (3) Prior to payment of the Disbursement Amount by the
                  Purchaser to the Escrow Agent with respect to the initial Wet
                  Funding, Purchaser has obtained confirmation from the
                  receiving bank that the information pertaining to it on the
                  Escrow Agent Standing Wire Instructions is accurate.

                        (4) With respect to each Wet Funding, simultaneously
                  with the payment by Purchaser of the Disbursement Amount for a
                  Mortgage Loan in accordance with the Escrow Agent Standing
                  Wire Instructions, (i) the related Seller hereby conveys to
                  Purchaser all of such Seller's right, title and interest in,
                  to and under such Mortgage Loan (including, without
                  limitation, Servicing Rights with respect thereto), free and
                  clear of all liens, pledges, charges, encumbrances or security
                  interests of any nature, and (ii) such Seller hereby covenants
                  to cause to occur a Collateral Receipt by the Scheduled
                  Collateral Receipt Date and to provide Purchaser with a
                  Conversion Loan Purchase Detail for any Collateral Receipt
                  relating to a Conduit Submission Package.

                        (5) With respect to each Wet Funding, if by the
                  Scheduled Collateral Receipt Date (i) a Collateral Receipt has
                  occurred and (ii) the related Seller is not in breach of this
                  Agreement, the Electronic Tracking Agreement or the Custodial
                  Agreement then (a) with respect to any Collateral Receipt
                  containing a Dry Submission Package, a Collateral Receipt
                  Adjustment will occur and (b) with respect to any Collateral
                  Receipt containing a Conduit Submission Package a Repurchase
                  will occur. If a Collateral Receipt does not occur by the
                  Scheduled Collateral Receipt Date Purchaser may elect a remedy
                  pursuant to Section 7 including, without limitation, the
                  application of an Incremental Pass-Through Rate.

            (c) Specific Procedures for Purchases of Mortgage Loans related to
Dry Fundings structured as Closing Transactions.

                        (1) Prior to Purchaser's election to purchase any
                  Mortgage Loan pursuant to a Dry Funding structured as a
                  Closing Transaction, Purchaser shall have received from the
                  related Seller (i) a Closing Loan Purchase Detail in
                  electronic format, (ii) a Request to Purchase, in the form
                  attached hereto as Exhibit Y, signed by an Authorized
                  Signatory of such Seller, (iii) a MERS Report reflecting the
                  Purchaser as Investor or Interim Funder for each MERS
                  Designated Loan, (iv) evidence that the Cash Account Balance
                  is not less than the sum of the Supplemental Amount plus the
                  Wire Fee and (v) evidence that Custodian has received all
                  applicable documents required by Section 2 of the Custodial
                  Agreement. The terms and conditions of each such purchase
                  shall be set forth in this Agreement and in the applicable
                  Funding Confirmation.


                                       17
<PAGE>

                        (2) If Purchaser elects to purchase any Mortgage Loan
                  pursuant to a Dry Funding structured as a Closing Transaction,
                  Purchaser shall (i) withdraw the Supplemental Amount, if any,
                  and the Wire Fee from the Cash Account and (ii) pay the
                  Disbursement Amount for such Mortgage Loans to the Escrow
                  Agent by wire transfer of immediately available funds in
                  accordance with the Escrow Agent Standing Wire Instructions.

                        (3) Prior to payment of the Disbursement Amount by the
                  Purchaser to the Escrow Agent with respect to the initial Dry
                  Funding, Purchaser has obtained confirmation from the
                  receiving bank that the information pertaining to it on the
                  Escrow Agent Standing Wire Instructions is accurate.

                        (4) With respect to each Dry Funding structured as a
                  Closing Transaction, simultaneously with the payment by
                  Purchaser of the Disbursement Amount for a Mortgage Loan in
                  accordance with the Escrow Agent Standing Wire Instructions,
                  the related Seller hereby conveys to Purchaser all of such
                  Seller's right, title and interest in, to and under such
                  Mortgage Loan (including, without limitation, Servicing Rights
                  with respect thereto), free and clear of all liens, pledges,
                  charges, encumbrances or security interests of any nature.

                        (5) With respect to each Dry Funding structured as a
                  Closing Transaction, if a Repurchase has not occurred by the
                  Scheduled Repurchase Date and if the related Seller has not
                  repurchased the related Mortgage Loan(s), Purchaser may elect
                  a remedy pursuant to Section 7 including, without limitation,
                  the application of an Incremental Pass-Through Rate.

            (d) Specific Procedures for Purchases of Mortgage Loans related to
Dry Fundings structured as Rewarehousing Transactions.

                        (1) Prior to Purchaser's election to purchase any
                  Mortgage Loan pursuant to a Dry Funding structured as a
                  Rewarehousing Transaction, Purchaser shall have received from
                  the related Seller (i) a Rewarehousing Loan Purchase Detail in
                  electronic format and (ii) a Request to Purchase, in the form
                  attached hereto as Exhibit Y, signed by an Authorized
                  Signatory of such Seller, (iii) an original of a Warehouse
                  Lender's Release or such Seller's Release, as applicable, (iv)
                  a MERS Report reflecting the Purchaser as Investor or Interim
                  Funder for each MERS Designated Loan, (v) evidence that the
                  Cash Account Balance is not less than the sum of the
                  Supplemental Amount plus the Wire Fee and (vi) evidence that
                  the Custodian has received all applicable documents required
                  by Section 2 of the Custodial Agreement. The terms and
                  conditions of each such purchase shall be set forth in this
                  Agreement and in the applicable Funding Confirmation.


                                       18
<PAGE>

                        (2) If Purchaser elects to purchase any Mortgage Loan
                  pursuant to a Dry Funding structured as a Rewarehousing
                  Transaction, Purchaser shall (i) withdraw the Supplemental
                  Amount and the Wire Fee, in each case if any, from the Cash
                  Account and (ii) pay the Disbursement Amount for such Mortgage
                  Loans to the Warehouse Lender or such Seller, as applicable,
                  by wire transfer of immediately available funds in accordance
                  with the Warehouse Lender's Wire Instructions or such Seller's
                  Wire Instructions, as applicable.

                        (3) With respect to each Dry Funding structured as a
                  Rewarehousing Transaction, simultaneously with the payment by
                  Purchaser of the Disbursement Amount for a Mortgage Loan, in
                  accordance with the Warehouse Lender's Wire Instructions or
                  the related Seller's Wire Instructions, as applicable, such
                  Seller hereby conveys to Purchaser all of such Seller's right,
                  title and interest in, to and under such Mortgage Loan
                  (including, without limitation, Servicing Rights with respect
                  thereto), free and clear of all liens, pledges, charges,
                  encumbrances or security interests of any nature.

                        (4) With respect to each Dry Funding structured as a
                  Rewarehousing Transaction, if a Repurchase has not occurred by
                  the Scheduled Repurchase Date and if the related Seller has
                  not repurchased the related Mortgage Loan(s), Purchaser may
                  elect a remedy pursuant to Section 7 including the application
                  of an Incremental Pass-Through Rate.

            Section 3. Procedure for Repurchases of Mortgage Loans.

            (a) Prior to the related Seller's repurchase of any Mortgage Loan
that such Seller intends to subsequently offer for sale to Purchaser under the
Conduit Funding Program and at least five Business Days prior to such Seller's
repurchase of any Mortgage Loan that such Seller intends to offer for sale to
Purchaser under the MBS Swap Funding Program, all agreements related to the
applicable UBSRES Purchase Program must be executed by such Seller, the
Purchaser and where applicable the Custodian, and all requirements of such
agreements must be satisfied as a condition precedent to the following:

            (i) For Mortgage Loans that the related Seller intends to repurchase
      and offer to Purchaser under the Conduit Purchase Program, the following
      must occur on or before the Scheduled Repurchase Date:

                        (1) Such Seller shall transmit electronically a
                  Conversion Loan Purchase Detail containing all information set
                  forth on Exhibit C hereto to Purchaser and Custodian shall
                  have received all applicable documents required by Section 2
                  of the Custodial Agreement to be in a Conduit Submission
                  Package;

                        (2) Such Seller shall remit the Repurchase Price to
                  Purchaser and Purchaser shall assign, transfer and convey to
                  such Seller all of


                                       19
<PAGE>

                  Purchaser's right, title and interest in, to and under such
                  Mortgage Loan, free and clear of all liens, pledges, charges,
                  claims, encumbrances or security interests of any nature; and

                        (3) Purchaser shall remit the Purchase Price to such
                  Seller pursuant to, and to the extent provided for under, the
                  terms of the Conduit Funding Program and such Seller shall
                  assign, transfer and convey to Purchaser pursuant to the
                  applicable UBSRES Purchase Program all of such Seller's right,
                  title and interest in, to and under such Mortgage Loan, free
                  and clear of all liens, pledges, charges, claims, encumbrances
                  or security interests of any nature.

            The payment of funds pursuant to clauses (2) and (3) above shall be
netted.

            (ii) For Mortgage Loans that the related Seller intends to
      repurchase and subsequently offer for sale to Purchaser under the MBS Swap
      Funding Program the following must occur on or before the Scheduled
      Repayment Date:

                  (1) Such Seller shall transmit to Purchaser, via a facsimile
            transmission, the applicable MBS Swap Shipment Documents at least
            five (5) Business Days before the Scheduled Repurchase Date;

                  (2) Purchaser shall deliver to the Custodian a Request for
            Mortgage Loan Shipment setting for the Mortgage Loans to be shipped
            and the location to which such Mortgage Loans shall be delivered via
            overnight courier;

                  (3) Such Seller shall deliver to Purchaser, via overnight
            courier, the related MBS Swap Submission Package;

                  (4) Upon Purchaser's review of the MBS Swap Submission Package
            and election to purchase such Mortgage Loans, such Seller shall
            remit the Repurchase Price to Purchaser and Purchaser shall assign,
            transfer and convey to such Seller all of Purchaser's right, title
            and interest in, to and under such Mortgage Loan, free and clear of
            all liens, pledges, charges, claims, encumbrances or security
            interests of any nature; and

                  (5) Purchaser shall remit the purchase price to such Seller
            pursuant to, and to the extent provided for under, the terms of the
            MBS Swap Purchase Program and such Seller shall assign, transfer and
            convey to Purchaser pursuant to the UBSRES Purchase Program all of
            such Seller's right, title and interest in, to and under such
            Mortgage Loan, free and clear of all liens, pledges, charges,
            claims, encumbrances or security interests of any nature.

            The payment of funds pursuant to clauses (4) and (5) above shall be
netted.


                                       20
<PAGE>

            (b) With respect to any Wet Mortgage Loan or Dry Mortgage Loan, if
the related Seller has provided Purchaser with an MBS Swap Funding Program
Selection Notice and such Seller, subsequent to such delivery and subsequent to
the Scheduled Repurchase Date for such Mortgage Loan, provides Purchaser with a
Conversion Loan Purchase Detail and a corresponding Conduit Submission Package,
then Purchaser may elect a remedy pursuant to Section 7 and may retroactively
apply an Incremental Pass-Through Rate for such Mortgage Loan for the period
from the Scheduled Repurchase Date through one day prior to the Repurchase Date.

            (c) With respect to each Mortgage Loan, on either the Scheduled
Collateral Receipt Date or the Scheduled Repurchase Date, if the related Seller
has not satisfied the requirements of this Agreement or Purchaser has elected
not to purchase such Mortgage Loan:

            (i) the Pass-Through Rate shall increase by the Incremental
      Pass-Through Rate;

            (ii) such Seller shall remit the Repurchase Price to Purchaser and
      Purchaser shall assign, transfer and convey to such Seller all of
      Purchaser's right, title and interest in, to and under such Mortgage Loan,
      free and clear of all liens, pledges, charges, claims, encumbrances or
      security interests of any nature; and

            (iii) upon receipt of the Repurchase Price and such Seller's
      Delivery Instructions from such Seller, Purchaser shall direct Custodian
      to deliver the Dry Submission Package or Conduit Submission Package
      related to such Mortgage Loan pursuant to such Seller's Delivery
      Instructions.

            Section 4. Terms of Each Transaction.

            (a) The obligations of the parties hereto shall, with respect to
each Transaction, begin on a Purchase Date and terminate on the Repurchase Date
or on the satisfaction by the related Seller of its obligations pursuant to
Section 7.

            (b) The terms and conditions of each Transaction, including, without
limitation, the Purchase Date, the Scheduled Repurchase Date, the Mortgage Loan
subject thereto, the Purchase Price, the Pass-Through Rate, the Incremental
Pass-Through Rate, the Scheduled Collateral Receipt Date for Wet Fundings only,
the Custodial Fee and, if applicable, the Wire Fee, shall be set forth in the
related Funding Confirmation. Each Funding Confirmation shall be deemed to be
controlling as to the related terms and provisions of the purchase of a Mortgage
Loan, absent manifest error, without regard to any other oral or written
communication between Purchaser and the related Seller with respect to the
purchase of such Mortgage Loan. With respect to the purchase or repurchase of a
Mortgage Loan, in the event of any conflict between the terms and the provisions
of this Agreement and the terms and provisions of the related Funding
Confirmation, the terms and provisions of the related Funding Confirmation will
prevail over the terms and provisions of this Agreement.

            Section 5. Cash Account.


                                       21
<PAGE>

            (a) The Sellers hereby authorize and direct Purchaser to create a
separate Cash Account for the Sellers. The Cash Account shall be held by
Purchaser for the Sellers subject to the terms and conditions of this Agreement.
Purchaser shall notify the Sellers, via electronic or facsimile transmission, of
the Cash Account Balance on each Business Day when the Cash Account Balance is
greater than zero and on each Business Day on which a Transaction occurs
hereunder.

            (b) Purchaser shall credit the Cash Account for (i) any deposits
therein by the related Seller upon such Seller's written direction pursuant to a
Withdrawal/Deposit Notice, (ii) any amounts due the related Seller and payable
by Purchaser under any UBSRES Purchase Program to the extent not otherwise
netted as described in Section 3 of this Agreement, (iii) any Supplemental
Amount for any of the Sellers' Mortgage Loans upon the refunding to Purchaser of
the Disbursement Amount for such Mortgage Loan by the Escrow Agent upon any
failure to apply the Disbursement Amount in connection with the proposed funding
of such Mortgage Loan, (iv) any credit pursuant to a Cash Account Adjustment,
(v) any Cash Account Interest Accruals and (vi) any deposits by the Sellers
pursuant to Section 7 hereof.

            (c) Purchaser shall debit the Cash Account for (i) any withdrawals
therefrom by the Sellers upon written direction pursuant to a Withdrawal/Deposit
Notice from each Seller, (ii) any amounts due Purchaser and payable by the
Sellers under any UBSRES Purchase Program, (iii) the Supplemental Amount for any
Mortgage Loan upon payment of the Disbursement Amount for such Mortgage Loan to
the Escrow Agent in accordance with Section 2(b)(2), Section 2(c)(1) and Section
2(d)(2), (iv) any debit pursuant to a Cash Account Adjustment and (v) any Wire
Fees.

            (d) Upon termination of this Agreement and payment in full of all
obligations owing by the related Seller hereunder, under the Custodial Agreement
and under the Electronic Tracking Agreement, Purchaser shall remit to the
Sellers the Cash Account Balance.

            Section 6. Servicing of the Mortgage Loans.

            (a) It is expressly acknowledged that the Servicing Rights relating
to each Mortgage Loan purchased by Purchaser hereunder have been or will be
sold, assigned, and transferred by the related Seller to Purchaser along with
such Mortgage Loan. The related Seller shall service and administer each
Mortgage Loan on behalf of Purchaser on an interim basis in accordance with
accepted and prudent mortgage loan servicing standards and procedures generally
accepted in the mortgage banking industry for the same type of mortgage loans as
the Mortgage Loans and in a manner at least equal in quality to the servicing
such Seller provides for mortgage loans which it owns, provided that such Seller
shall at all times comply with applicable law and the requirements of any
applicable insurer or guarantor so that the insurance and any applicable
guarantee in respect of any Mortgage Loan is not voided or reduced. The related
Seller shall at all times maintain accurate and complete records of its
servicing of each Mortgage Loan, and Purchaser may, at any time during such
Seller's business hours, on reasonable notice, examine and make copies of such
records. On the 2nd day of each calendar month, or at any other time upon
Purchaser's request such Seller shall deliver to Purchaser reports regarding the
status of each Mortgage Loan in accordance with Section 11(o) and Section 11(p),
which shall include, with respect to any MERS Designated Mortgage Loan, MERS
Reports, and any


                                       22
<PAGE>

circumstances that could materially adversely affect any such Mortgage Loan,
Purchaser's ownership of any such Mortgage Loan or the collateral securing any
such Mortgage Loan. The related Seller agrees and acknowledges that Purchaser
may, at any time, terminate the servicing of the Mortgage Loans by such Seller
and transfer servicing to another Person on such date as Purchaser may determine
in its sole discretion. In the event that anything in this Agreement is
interpreted as constituting one or more interim servicing contracts, each such
servicing contract shall terminate automatically upon the earliest of (i) an
Event of Default, (ii) the repurchase of a Mortgage Loan by the related Seller
or (iii) the Purchaser's notice to the related Seller directing such Seller to
transfer servicing (provided, such Seller's obligations as set forth herein to
cooperate in the transfer of such servicing shall not terminate until such
servicing has actually been transferred in full).

            (b) Within five Business Days of notice from Purchaser, or
immediately upon notice if an Event of Default has occurred:

            (i) the Sellers shall establish and maintain a Custodial Account
      entitled "[name of Seller(s)], in trust for UBS Real Estate Securities
      Inc. and its assignees under the Amended and Restated Mortgage Loan
      Repurchase Agreement dated as of the date of this Agreement" and shall
      promptly deposit into the Custodial Account, in the form received with any
      necessary endorsements, all collections received in respect of each
      Mortgage Loan that are payable to Purchaser as the owner of each such
      Mortgage Loan; and

            (ii) at the Purchaser's sole option, upon written notice from the
      Purchaser, the related Seller shall transfer servicing of its Mortgage
      Loans to a successor servicer designated by the Purchaser.

            (c) Amounts deposited in the Custodial Account with respect to any
Mortgage Loan shall be held in trust for Purchaser as the owner of such Mortgage
Loan and shall be released only as follows:

            (i) All amounts deposited in the Custodial Account with respect to a
      Seller's Mortgage Loans shall be paid to such Seller upon the repurchase
      by such Seller of the related Mortgage Loans from Purchaser if, and to the
      extent that, the Repurchase Prices and all other amounts due and payable
      to Purchaser hereunder with respect to such Mortgage Loans have been paid.
      The amounts paid to such Seller (if any) pursuant to this Section 6(c)(i)
      shall constitute such Seller's sole compensation for servicing the
      Mortgage Loans as provided in this Section 6.

            (ii) If a Successor Servicer is appointed by Purchaser (either under
      the circumstances set forth in clause (b)(ii) above, Section 7 or
      otherwise), or if an Event of Default has occurred, all amounts deposited
      in the Custodial Account shall be paid to Purchaser promptly upon such
      delivery.

            (iii) During the period that the related Seller acts as Servicer,
      all amounts deposited in the Custodial Account shall be released only in
      accordance with Purchaser's written instructions.


                                       23
<PAGE>

            (d) In the event the related Seller or its Affiliate is servicing
the Mortgage Loans, such Seller shall permit the Purchaser to inspect such
Seller's or its Affiliate's servicing facilities, as the case may be, for the
purpose of satisfying the Purchaser that such Seller or its Affiliate, as the
case may be, has the ability to service the Mortgage Loans as provided in this
Agreement.

            (e) If the servicer of the Mortgage Loans is the related Seller or
the Servicer is an Affiliate of such Seller, such Seller shall provide to
Purchaser a letter from such Seller or such Affiliate, as the case may be, to
the effect that upon 1 day's notice from Purchaser or immediately upon the
occurrence of an Event of Default, Servicer's rights and obligations to service
the Mortgage Loans shall terminate immediately, without any further notice or
action by Purchaser and Servicer shall transfer servicing to Purchaser's
designee, at no cost or expense to the Purchaser, it being agreed that such
Seller will pay any and all fees required to terminate the Servicing Agreement
and to effectuate the transfer of servicing to the designee of the Purchaser.

            Section 7. Remedies; Margin Deficits.

            (a) Upon the occurrence of an Event of Default, at the option of
Purchaser exercised by written notice to the related Seller (which option shall
be deemed to have been exercised even if no notice is given, immediately upon
the occurrence of an Act of Insolvency with respect to such Seller or an
Affiliate of such Seller), the Scheduled Repurchase Date for each Transaction of
such Seller hereunder shall be, deemed immediately to occur and, upon exercise
of such option, (i) such Seller's obligations hereunder to repurchase all of its
Mortgage Loans shall thereupon become immediately due and payable, (ii) the
Pass-Through Rate applicable to each such Mortgage Loan shall increase by the
Incremental Pass-Through Rate, (iii) all amounts then or thereafter held in the
Custodial Account and the Cash Account shall be retained by Purchaser and
applied to the aggregate unpaid Repurchase Prices owed by such Seller and to any
other amounts owing by such Seller hereunder or under the Custodial Agreement
and (iv) Purchaser may at any time on the Business Day following notice to
Seller (which notice may be the notice given above of an Event of Default), (A)
immediately sell, without demand or further notice of any kind, at a public or
private sale and at such price or prices as Purchaser may deem satisfactory, any
or all of such Mortgage Loans and apply the proceeds thereof (net of any
expenses of sale) to the aggregate unpaid Repurchase Prices and any other
amounts owing by such Seller hereunder or under the Custodial Agreement or (B)
in its sole discretion elect, in lieu of selling all or a portion of such
Mortgage Loans, to give such Seller credit for such Mortgage Loans in an amount
equal to the price therefor on such date, obtained from a generally recognized
source or the most recent closing bid quotation from such a source, against the
aggregate unpaid Repurchase Prices and any other amounts owing by Seller
hereunder or under the Custodial Agreement, and in either case upon the
determination and receipt by Purchaser of all such amounts owing by such Seller
(including, without limitation, any unpaid fees, expenses, legal fees and
expenses of Purchaser's counsel or other amounts owing to Purchaser under this
Agreement, the Electronic Tracking Agreement or the Custodial Agreement),
Purchaser shall transfer any remaining portion of such Mortgage Loans and
proceeds thereof to either (1) such Seller, if in Purchaser's reasonable
judgment such Seller is legally entitled thereto, (2) such other entity as is in
Purchaser's reasonable judgment legally entitled thereto or (3) if Purchaser
cannot determine in its judgment the entity entitled thereto, a court of
competent jurisdiction; provided that such Seller shall be liable for any
deficiency if the


                                       24
<PAGE>

proceeds of any sale or other disposition of the Mortgage Loans and any amounts
applied from the Custodial Account and the Cash Account are insufficient to pay
all amounts to which Purchaser is entitled hereunder.

            (b) If any Mortgage Loan becomes a Defective Mortgage Loan prior to
the Repurchase Date, the Pass-Through Rate applicable to such Defective Mortgage
Loan shall increase by the Incremental Pass-Through Rate, and Purchaser, at its
election, may immediately accelerate the Scheduled Repurchase Date and require
that the related Seller, upon receipt of such election, immediately repurchase
such Defective Mortgage Loan by remitting to Purchaser (in immediately available
funds in accordance with Purchaser's Wire Instructions) the Repurchase Price for
such Defective Mortgage Loan.

            (c) If the related Seller fails to comply with its obligations in
the manner described in Section 7(b) or under the Electronic Tracking Agreement
or if the Purchaser delivers notice to such Seller pursuant to Section 6(a) or
6(b) hereof such Seller's rights and obligations to interim service Mortgage
Loans, as provided in this Agreement, shall terminate. If any such event occurs,
such Seller's rights and obligations to service the Mortgage Loans, as provided
in this Agreement, shall terminate immediately, without any further notice or
action by Purchaser. Upon any such termination, Purchaser is hereby authorized
and empowered to sell and transfer such rights to service the Mortgage Loans for
such price and on such terms and conditions as Purchaser shall determine in its
sole discretion. The related Seller does not have any right to and shall not
attempt to sell or transfer the Servicing Rights or any rights incident thereto
without the prior consent of the Purchaser, which may be withheld in Purchaser's
sole discretion. In the event of any servicing transfer, the related Seller
shall perform all acts and take all action so (i) that the Mortgage Loans and
all files and documents relating to such Mortgage Loans held by such Seller,
together with all escrow amounts relating to such Mortgage Loans, are delivered
to a Successor Servicer, (ii) all applicable laws and regulations relating to
the servicing of the Mortgage Loans and any transfer of the such servicing with
respect thereto are complied with in all respects, including, without limitation
all provisions of RESPA, the Truth in Lending Act and other applicable laws and
(iii) with respect to all MERS Designated Mortgage Loans, the "Servicer" and all
other relevant fields in the MERS(R) System are modified to reflect the
Successor Servicer, where applicable. To the extent that the approval of any
other insurer or guarantor is required for any such sale or transfer, the
related Seller shall fully cooperate with Purchaser to obtain such approval.
Upon exercise, by Purchaser of its remedies under this Section 7(c), the related
Seller hereby authorizes Purchaser to receive all amounts paid by any purchaser
of such rights to service the Mortgage Loans and to remit such amounts to such
Seller subject to Purchaser's rights of set-off under this Agreement.

            (d) Each Mortgage Loan required to be delivered to a Successor
Servicer by Section 7(c) shall be delivered free of any Servicing Rights in
favor of the related Seller and free of any title, interest, lien, encumbrance
or claim of any kind of such Seller, and such Seller shall deliver or cause to
be delivered all files and documents relating to each Mortgage Loan held by such
Seller to a Successor Servicer. The related Seller shall promptly take such
actions and furnish to Purchaser such documents that Purchaser deems necessary
or appropriate to enable Purchaser to cure any defect in each such Mortgage Loan
or to enforce such Mortgage Loans, as appropriate.


                                       25
<PAGE>

            (e) Each Seller agrees to indemnify and hold Purchaser and its
assigns harmless for and against all Losses resulting from or relating to any
Event of Default related to such Seller.

            (f) No election by Purchaser pursuant to this Section 7 shall
relieve the related Seller of responsibility or liability for any breach of or
under this Agreement.

            (g) Each Seller and its Affiliates hereby grant Purchaser and its
Affiliates a right of set-off, to secure the payment of any amounts that may be
due and payable to Purchaser from such Seller, such right to be upon any and all
monies or other property of such Seller and its Affiliates held or received by
Purchaser and its Affiliates, or due and owing from Purchaser and its Affiliates
to such Seller and its Affiliates.

            (h) If at any time the aggregate Asset Value of the Mortgage Loans
is less than the aggregate Purchase Price for all such Mortgage Loans (a "Margin
Deficit"), then Purchaser may by notice to the Sellers (as such notice is more
particularly set forth below, a "Margin Deficit Notice"), accelerate the
Scheduled Repurchase Date for the Mortgage Loans or require the Sellers to
deposit into the Cash Account an amount (which amount may be deposited in the
form of United States treasury obligations approved by the Purchaser) equal to
the Margin Deficit so that the aggregate Asset Value of the Mortgage Loans,
including any such amounts deposited into the Cash Account, will thereupon equal
or exceed the aggregate Asset Value. If Purchaser delivers a Margin Deficit
Notice to the Sellers on or prior to 10:00 a.m. (New York City time) on any
Business Day, then the Sellers shall repurchase the specified Mortgage Loans or
deposit an amount equal to the Margin Deficit into the Cash Account no later
than 5:00 p.m. (New York City time) on such Business Day. In the event Purchaser
delivers a Margin Deficit Notice to the Sellers after 10:00 a.m. (New York City
time) on any Business Day, then such Margin Deficit Notice shall be deemed to
have been delivered on the following Business Day and the Sellers shall be
required to repurchase the specified Mortgage Loans or deposit an amount equal
to the Margin Deficit into the Cash Account no later than 5:00 p.m. (New York
City time) on such subsequent Business Day.

            Section 8. Transfer of Mortgage Loan by Purchaser. Purchaser may, in
its sole discretion, grant or assign a security interest in any Mortgage Loan
sold by the related Seller hereunder and all rights of Purchaser under this
Agreement, the Electronic Tracking Agreement and/or the Custodial Agreement, in
respect of such Mortgage Loan to Assignee, subject only to an obligation on the
part of Assignee to deliver each such Mortgage Loan to Purchaser to permit
Purchaser or its designee to make delivery thereof to such Seller on the
Repurchase Date. It is anticipated that such assignment to Assignee will be made
by Purchaser, and each Seller hereby irrevocably consents to such assignment. No
notice of such assignment shall be given by Purchaser to any Seller. Assignment
by Purchaser of the Mortgage Loans as provided in this Section 8 shall not
release Purchaser from its obligations otherwise under this Agreement.

            Without limitation of the foregoing, an assignment of a Mortgage
Loan to Assignee, as described in this Section 8, shall be effective upon
delivery to Assignee of a Dry Submission Package.


                                       26
<PAGE>

            Section 9. Record Title to Mortgage Loans; Intent of Parties;
Security Interest.

            (a) From and after the delivery of the related Submission Package,
and subject to the remedies of Purchaser set forth in Section 7, the related
Seller shall remain the named payee or endorsee of each related Mortgage Note
and the mortgagee or assignee of record of each Mortgage (except with respect to
a MERS Designated Mortgage Loan) in trust for the benefit of Purchaser, for the
sole purpose of facilitating the servicing of such Mortgage Loan.

            (b) Each Seller shall maintain a complete set of books and records
for each of its Mortgage Loans which shall be clearly marked to reflect the
ownership interest in each Mortgage Loan of Purchaser and with respect to each
MERS Designated Mortgage Loan, such Seller shall designate the Purchaser as the
Investor and Interim Funder on the MERS(R) System.

            (c) Purchaser and each Seller confirm that the Transactions
contemplated herein are intended to be sales of the Mortgage Loans by such
Seller to Purchaser rather than borrowings secured by the Mortgage Loans. In the
event, for any reason, any Transaction is construed by any court or regulatory
authority as a borrowing rather than as a sale, each Seller and Purchaser intend
that Purchaser or Assignee, as the case may be, shall have a perfected first
priority security interest in the Collateral, free and clear of adverse claims.
In such case, such Seller shall be deemed to have hereby granted to Purchaser or
Assignee, as the case may be, a first priority security interest in and lien
upon the Collateral, free and clear of adverse claims. In such event, this
Agreement shall constitute a security agreement, the Custodian shall be deemed
to be an independent custodian for purposes of perfection of the security
interest granted to Purchaser or Assignee, as the case may be, and Purchaser or
Assignee, as the case may be, shall have all of the rights of a secured party
under applicable law. The related Seller shall, not later than the date of the
first purchase of a Mortgage Loan by Purchaser under this Agreement, deliver to
Purchaser a UCC-1 Financing Statement containing a description of collateral in
the form attached hereto in Exhibit I.

            Section 10. Representations and Warranties.

            (a) Each Seller hereby represents and warrants to Purchaser as of
the date hereof and as of the date of each delivery of a Submission Package
that:

            (i) Such Seller is duly organized, validly existing and in good
      standing under the laws of the state of its organization or of the United
      States of America and has all licenses necessary to carry on its business
      as now being conducted and is licensed, qualified and in good standing to
      do business in each jurisdiction in which it is legally required to do so.
      Such Seller has all requisite power and authority (including, if
      applicable, corporate power) to execute and deliver this Agreement, the
      Electronic Tracking Agreement and the Custodial Agreement and to perform
      in accordance herewith and therewith; the execution, delivery and
      performance of this Agreement, the Electronic Tracking Agreement and the
      Custodial Agreement (including all instruments of transfer to be delivered
      pursuant to this Agreement, the Electronic Tracking Agreement and the
      Custodial Agreement) by such Seller and the consummation of the
      transactions contemplated hereby and thereby have been duly and validly
      authorized. Each of this


                                       27
<PAGE>

      Agreement, the Electronic Tracking Agreement and the Custodial Agreement
      evidences the valid, binding and enforceable obligation of such Seller and
      all requisite action (including, if applicable, corporate action) has been
      taken by such Seller to make this Agreement, the Electronic Tracking
      Agreement and the Custodial Agreement valid and binding upon such Seller
      in accordance with its terms;

            (ii) No approval of the transactions contemplated by this Agreement,
      the Electronic Tracking Agreement or the Custodial Agreement from the OTS,
      the NCUA, the FDIC or any similar federal or state regulatory authority
      having jurisdiction over Seller is required, or if required, such approval
      has been obtained. The transfers, assignments and conveyances provided for
      herein and therein are not subject to the bulk transfer or any similar
      statutory provisions in effect in any applicable jurisdiction;

            (iii) The consummation of the transactions contemplated by this
      Agreement, the Electronic Tracking Agreement and the Custodial Agreement
      are in the ordinary course of business of Seller and will not result in
      the breach of any term or provision of the charter, by-laws or other
      organizational document of Seller or result in the breach of any term or
      provision of, or conflict with or constitute a default under or result in
      the acceleration of any obligation under, an agreement, indenture or loan
      or credit agreement or other instrument to which Seller or its property is
      subject, or result in the violation of any law, rule, regulation, order,
      judgment or decree to which Seller or its property is subject;

            (iv) This Agreement, the Custodial Agreement, the Electronic
      Tracking Agreement and every document to be executed by Seller pursuant
      hereto and thereto is and will be valid, binding and a subsisting
      obligation of Seller, enforceable in accordance with its respective terms.
      No consents or approvals are required to be obtained by Seller or its
      Parent Company for the execution, delivery and performance of this
      Agreement, the Electronic Tracking Agreement or the Custodial Agreement by
      Seller;

            (v) All information relating to Seller that Seller has delivered or
      caused to be delivered to Purchaser, including, but not limited to, all
      documents related to this Agreement, the Electronic Tracking Agreement,
      the Custodial Agreement or Seller's financial statements, and all such
      information hereafter furnished by Seller, does not and will not contain
      any untrue statement of a material fact or omit to state a material fact
      necessary to make the statements made therein or herein in light of the
      circumstances under which they were made, not misleading. Seller has
      disclosed in writing any and all facts relating to Seller that materially
      and adversely affect or may affect the business operations or financial
      condition of Seller or the ability of Seller to perform its obligations
      under this Agreement, the Electronic Tracking Agreement or the Custodial
      Agreement;

            (vi) There are no actions, suits or proceedings pending, or to the
      knowledge of Seller threatened, including any claims for which an action,
      suit or proceeding has not been commenced, against or affecting Seller or
      any of its assets in any court or before any arbitrator or before any
      governmental commission, board, bureau or other administrative agency
      that, in any such case, if adversely determined, would have a


                                       28
<PAGE>

      material adverse effect on the financial condition or business of Seller
      or the ability of Seller to perform under this Agreement, the Electronic
      Tracking Agreement, each Funding Confirmation and the Custodial Agreement;

            (vii) Seller and its Subsidiaries have filed all Federal income tax
      returns and all other material tax returns that are required to be filed
      by them and have paid all taxes due pursuant to such returns or pursuant
      to any assessment received by it or any of its Subsidiaries, except for
      any such taxes as are being appropriately contested in good faith by
      appropriate proceedings diligently conducted and with respect to which
      adequate reserves have been provided. The charges, accruals and reserves
      on the books of Seller and its Subsidiaries in respect of taxes and other
      governmental charges are, in the opinion of Seller, adequate;

            (viii) Neither Seller nor any of its Subsidiaries is an "investment
      company", or a company "controlled" by an "investment company", within the
      meaning of the Investment Company Act of 1940, as amended;

            (ix) Upon the filing of financing statements on Form UCC-1 naming
      Purchaser as "Secured Party", Seller as "Debtor" and describing the
      Mortgage Loans, in the jurisdictions and recording offices listed on
      Exhibit V attached hereto, the security interests granted hereunder in the
      Mortgage Loans of Seller will constitute fully perfected security
      interests under the Uniform Commercial Code in all right, title and
      interest of Seller in, to and under such Mortgage Loans, which can be
      perfected by filing under the Uniform Commercial Code;

            (x) As of the date hereof, and during the four months immediately
      preceding the Effective Date, Seller's chief executive office, is, and has
      been located at 520 Broadhollow Road, Melville, New York 11747. As of the
      date hereof, Seller's jurisdiction of organization is as follows: American
      Home Mortgage Investment Corp., Maryland, American Home Mortgage
      Acceptance, Inc., Maryland, American Home Mortgage Holdings, Inc.,
      Delaware, American Home Mortgage Corp., New York, and/or Columbia
      National, Incorporated, Maryland;

            (xi) the aggregate consolidated Tangible Net Worth of the Parent
      Company is not less than $75,000,000;

            (xii) Seller (and each servicer) is approved by GNMA as an approved
      issuer, Fannie Mae as an approved lender, Freddie Mac as an approved
      seller/servicer (as the case may be) and by FHA as an approved mortgagee
      and by VA as an approved VA lender, in each case in good standing (such
      collective approvals and conditions, "Agency Approvals"), with no event
      having occurred or Seller (or any subservicer) having any reason
      whatsoever to believe or suspect will occur prior to the purchase of the
      Mortgage Loan by the related Agency, including without limitation a change
      in insurance coverage which would either make Seller (or any servicer)
      unable to comply with the eligibility requirements for maintaining all
      such Agency Approvals or require notification to the relevant Agency or to
      HUD, FHA or VA. Should Seller (or any servicer), for any reason, cease to
      possess all such Agency Approvals, or should notification to the relevant
      Agency


                                       29
<PAGE>

      or to HUD, FHA or VA be required, Seller shall so notify Purchaser
      immediately in writing. Notwithstanding the preceding sentence, Seller
      shall take all necessary action to maintain all of its (and each
      servicer's) Agency Approvals at all times during the term of this
      Agreement. Seller (and any servicer) has adequate financial standing,
      servicing facilities, procedures and experienced personnel necessary for
      the sound servicing of mortgage loans of the same types as may from time
      to time constitute Mortgage Loans and in accordance with Accepted
      Servicing Practices;

            (xiii) The Custodian is an eligible custodian under the Agency Guide
      and Agency Program; and

            (xiv) As of the date hereof, with respect to the Original Repurchase
      Agreement, no Event of Default (as defined therein) has occurred and is
      continuing and the Original American Home Parties are not in default with
      respect to any of such Original American Home Parties' obligations
      thereunder.

            (b) With respect to each Mortgage Loan as of the related Purchase
Date, the related Seller hereby represents and warrants that the Mortgage Loan
has been originated with 30 days of the date such Mortgage Loan was first sold
to Purchaser hereunder and such Seller hereby makes each representation,
warranty and covenant set forth on Schedule 1 hereto.

            (c) Each Seller hereby represents and warrants to Purchaser as of
the date hereof and as of each Purchase Date, (i) with respect to the Escrow
Agent Wire Instructions, the Seller received such instructions on the letterhead
of the Escrow Agent and such instructions are true and correct and (ii) such
Seller has inserted the Closing Instruction Letter Insert in each Closing
Instruction Letter for all Wet Fundings and Dry Fundings structured as Closing
Transactions.

            (d) Each Seller hereby represents and warrants to Purchaser as of
the date hereof and as of each Purchase Date, with respect to each related Wet
Funding or Dry Funding structured as a Closing Transaction, an insured closing
letter from each Escrow Agent that is not a title insurance company is included
in the Credit File and such Seller shall promptly, upon request of Purchaser,
send to Purchaser (i) a copy of any such insured closing letter and (ii) a
complete list of all Escrow Agents such Seller has approved to act as an Escrow
Agent.

            (e) Each of American Home Mortgage Investment Corp. and American
Home Mortgage Acceptance, Inc. hereby represents, warrants and covenants to
Purchaser that it is a REIT Seller and it has not engaged in any material
"prohibited transactions" as defined in Section 857(b)(6)(B)(iii) and (C) of the
Code. Each REIT Seller for its current "tax year" (as defined in the Code) is
entitled to a dividends paid deduction under the requirements of Section 857 of
the Code with respect to any dividends paid by it with respect to each such year
for which it claims a deduction in its Form 1120-REIT filed with the United
States Internal Revenue Service for such year.

            The representations and warranties of each Seller in this Section 10
and Schedule 1 hereto are unaffected by and supersede any provision in any
endorsement of any


                                       30
<PAGE>

Mortgage Loan or in any assignment with respect to such Mortgage Loan to the
effect that such endorsement or assignment is without recourse or without
representation or warranty.

            Section 11. Covenants of the Sellers. Each Seller hereby covenants
and agrees with Purchaser as follows:

            (a) Such Seller shall deliver to Purchaser; UBS Real Estate
Securities Inc., 1285 Avenue of the Americas, 11th Floor, New York, New York
10019, Attention: Peter Chudy and Bill Boak:

            (i) Within 120 days after the end of each fiscal year of such
      Seller, consolidated balance sheets of such Seller and its consolidated
      subsidiaries and the related consolidated statements of income showing the
      financial condition of such Seller and its consolidated subsidiaries as of
      the close of such fiscal year, consolidated statement of cash flows, as of
      the close of such fiscal year, setting forth, in each case, in comparative
      form the corresponding figures for the preceding year, all the foregoing
      consolidated financial statements to be reported on by, and to carry the
      report (acceptable in form and content to Purchaser) of an independent
      public accountant of national standing acceptable to Purchaser;

            (ii) Within 45 days after the end of each of the first two months of
      each fiscal quarter of such Seller, unaudited consolidated balance sheets
      and consolidated statements of income, all to be in a form acceptable to
      Purchaser, showing the financial condition and results of operation of
      such Seller and its consolidated subsidiaries on a consolidated basis as
      of the end of each such month and for the then elapsed portion of the
      fiscal year, setting forth, in each case, in comparative form the
      corresponding figures for the corresponding periods of the preceding
      fiscal year, certified by a financial officer of such Seller (acceptable
      to Purchaser) as presenting fairly the financial position and results of
      operations of such Seller and its consolidated subsidiaries and as having
      been prepared in accordance with generally accepted accounting principles
      consistently applied, in each case, subject to normal year-end audit
      adjustments;

            (iii) Promptly upon receipt thereof, a copy of each other report
      submitted to such Seller by its independent public accountants in
      connection with any annual, interim or special audit of such Seller;

            (iv) Promptly upon becoming aware thereof, notice of (1) the
      commencement of, or any determination in, any legal, judicial or
      regulatory proceedings where damages, fines, penalties and/or other claims
      could reasonably be expected to be or are in excess of $250,000 (x)
      against such Seller or Parent Company or (y) where injunctive or other
      equitable relief is sought against such Seller or Parent Company, (2) any
      dispute between such Seller or its Parent Company and any governmental or
      regulatory body where damages, fines, penalties and/or other claims could
      reasonably be expected to be or are in excess of $250,000 (x) against such
      Seller or Parent Company or (y) where injunctive or other equitable relief
      is sought against such Seller or Parent Company, (3) any event or
      condition, which, in any case of (1) or (2), if adversely determined,
      would have a material adverse effect on (A) the validity or enforceability
      of


                                       31
<PAGE>

      this Agreement, (B) the financial condition or business operations of such
      Seller, or (C) the ability of such Seller to fulfill its obligations under
      this Agreement or (4) any material adverse change in the business,
      operations, prospects or financial condition of such Seller, including,
      without limitation, an Act of Insolvency with respect to such Seller or
      any Affiliate of such Seller;

            (v) Promptly upon becoming available, copies of all financial
      statements, reports, notices and proxy statements sent by its Parent
      Company, such Seller or any of such Seller's consolidated subsidiaries in
      a general mailing to their respective stockholders and of all reports and
      other material (including copies of all registration statements under the
      Securities Act of 1933, as amended) filed by any of them with any
      securities exchange or with the Securities and Exchange Commission or any
      governmental authority succeeding to any or all of the functions of said
      Commission;

            (vi) Promptly upon becoming available, copies of any press releases
      issued by its Parent Company or such Seller and copies of any annual,
      quarterly and monthly financial reports and any reports on Form H-(b)12
      which its Parent Company or such Seller may be required to file with the
      OTS or the RTC or comparable reports which a Parent Company or such Seller
      may be required to file with the FDIC or any other federal banking agency
      containing such financial statements and other information concerning such
      Parent Company's or such Seller's business and affairs as is required to
      be included in such reports in accordance with the rules and regulations
      of the OTS, the RTC, the FDIC or such other banking agency, as may be
      promulgated from time to time;

            (vii) Promptly upon becoming available, copies of any reports any
      REIT Seller may be required to file with the Internal Revenue Service;

            (viii) Such supplements to the aforementioned documents and such
      other information regarding the operations, business, affairs and
      financial condition of its Parent Company, such Seller or any of such
      Seller's consolidated subsidiaries as Purchaser may request;

            (ix) Prior to the date of any purchase of a Mortgage Loan by
      Purchaser hereunder, a copy of (1) the articles of incorporation,
      certificate of formation or other organizational documents of such Seller
      and any amendments thereto certified by the Secretary of State,
      Comptroller of Currency, Internal Revenue Service or similar official of
      such Seller's jurisdiction of organization, (2) a copy of such Seller's
      by-laws, operating agreement or other internal governing documents,
      together with any amendments thereto, (3) a copy of the resolutions
      adopted by such Seller's Board of Directors or a similar governing body
      authorizing such Seller to enter into this Agreement, the Electronic
      Tracking Agreement and the Custodial Agreement and authorizing one or more
      of such Seller's officers to execute the documents related to this
      Agreement, the Electronic Tracking Agreement and the Custodial Agreement,
      (4) a certificate of incumbency and signature of each officer of such
      Seller executing any document in connection with this Agreement, the
      Electronic Tracking Agreement and the Custodial Agreement; (5) a
      certificate reflecting each Authorized Signatory of such


                                       32
<PAGE>

      Seller, in the form of Exhibit N hereto and (6) one or more opinions of
      counsel to such Seller, substantially in the form of Exhibit U hereto; and

            (x) A Covenant Compliance Letter, substantially in the form of
      Exhibit X hereto, within 45 days after the end of each of the first eleven
      calendar months of each fiscal year, within 60 days after the end of each
      of the first three fiscal quarters of each fiscal year and within 120 days
      after the end of each fiscal year.

            (b) Such Seller will be solvent at all relevant times prior to, and
will not be rendered insolvent by, any sale of a Mortgage Loan to Purchaser.

            (c) Such Seller will not sell any Mortgage Loan to Purchaser with
any intent to hinder, delay or defraud any of such Seller's creditors.

            (d) Such Seller shall comply, in all material respects, with all
laws, rules and regulations to which it is or may become subject.

            (e) Such Seller shall not move its chief executive office from the
address referred to in Section 10 or change its jurisdiction of organization
unless it shall have provided Purchaser thirty (30) days' prior written notice
of such change.

            (f) Such Seller shall pay and discharge all taxes, assessments and
governmental charges or levies imposed on it or on its income or profits or on
any of its Property prior to the date on which penalties attach thereto, except
for any such tax, assessment, charge or levy the payment of which is being
contested in good faith and by proper proceedings and against which adequate
reserves are being maintained.

            (g) Such Seller shall, upon request of Purchaser, promptly execute
and deliver to Purchaser all such other and further documents and instruments of
transfer, conveyance and assignment, and shall take such other action as
Purchaser may require to more effectively transfer, convey, assign to and vest
in Purchaser and to put Purchaser in possession of the property to be
transferred, conveyed, assigned and delivered hereunder and otherwise to carry
out more effectively the intent of the provisions under this Agreement.

            (h) Immediately upon notice of a lien or any circumstance which
could give rise to a lien on the Mortgage Loans, such Seller will defend its
Mortgage Loans against, and will take such other action as is necessary to
remove, any lien, security interest or claim on or to such Mortgage Loans (other
than any security interest created under this Repurchase Agreement), and such
Seller will defend the right, title and interest of Purchaser in and to any of
such Mortgage Loans against the claims and demands of all persons whomsoever.

            (i) If during the term of a Transaction, such Seller gains
possession of a Submission Package that relates to the Transaction, such Seller
shall hold such Submission Package in trust for Purchaser, immediately notify
Purchaser of the specific Submission Package being held by such Seller and
promptly deliver such Submission Package via overnight courier in accordance
with Purchaser's instructions.


                                       33
<PAGE>

            (j) Such Seller covenants and agrees to take all actions required of
it in compliance with the terms of the Electronic Tracking Agreement.

            (k) The Parent Company shall maintain a consolidated Tangible Net
Worth which shall be not less than the greater of (i) $75,000,000 measured on a
quarterly basis (as at the end of each month) and (ii) (A) 85% of the
consolidated Tangible Net Worth of such Parent Company at the end of the most
recently completed fiscal year of such Parent Company plus (B) 50% of net
proceeds from issuance of equity securities during such fiscal year plus (C) 50%
of positive year to date consolidated net income.

            (l) [Reserved].

            (m) Parent Company shall not permit, for any period of four
consecutive calendar months (each such period, a "Test Period"), consolidated
Net Income for such Test Period, before income taxes for such Test Period and
distributions made during such Test Period, to be less than $1.00.

            (n) Such Seller shall, with respect to each Mortgage Loan, cause the
paragraphs set forth on Exhibit S hereto to be inserted into each closing letter
or other similar agreement with the Escrow Agent for such Mortgage Loan, and
shall, upon the request of Purchaser, fax a copy of such closing letter to
Purchaser prior to the closing of such Mortgage Loan.

            (o) Such Seller shall provide Purchaser with a monthly report, which
report shall include, among other items, a summary of such Seller's delinquency
and loss experience with respect to mortgage loans serviced by such Seller, any
Servicer or any designee of either, with respect to any MERS Designated Mortgage
Loan, MERS Reports, plus any such additional reports as Purchaser may reasonably
request with respect to such Seller's or any Servicer's servicing portfolio or
pending originations of mortgage loans. Such Seller shall not cause the Mortgage
Loans to be serviced by any servicer other than a servicer expressly approved in
writing by Purchaser.

            (p) On the second Business Day of each month, such Seller shall
furnish to Purchaser or shall cause the Servicer to furnish to Purchaser, a
remittance report, in hard copy and electronic format acceptable to Purchaser,
containing information regarding funds collected during the prior calendar
month. This report shall contain the following information:

            (i) Mortgage Loan number;

            (ii) Note Rate;

            (iii) Remittances allocable to principal and interest;

            (iv) Paid through date;

            (v) Mortgage Loan balance;

            (vi) Delinquency status;


                                       34
<PAGE>

            (vii) Whether the Mortgaged Property is in foreclosure or has become
      an real state owned property;

            (viii) Whether any Mortgagor is the subject of any bankruptcy
      action; and

            (ix) Any other information that Purchaser may reasonably request.

            (q) Such Seller covenants and agrees that it will not (1)
consolidate or merge or enter into any analogous reorganization or transaction
with any Person, unless such other Person is an Affiliate of Seller or is
engaged in the mortgage banking business and such Seller is the surviving
entity; (2) liquidate, wind up or dissolve (or suffer any liquidation or
dissolution); (3) cease actively to engage in the business of origination,
acquiring or servicing Mortgage Loans or make any other material change in the
nature or scope of the business in which such Seller engaged as of the date of
this Agreement; (4) sell, assign, lease, convey, transfer or otherwise dispose
of (whether in one transaction or a series of transactions) all or any
substantial part of such Seller's business or assets, whether now owned or
acquired after the date of this Agreement and without the prior written consent
of the Purchaser (except in the ordinary course of business or except in a
transaction or series of transactions between two or more Sellers); (5) acquire
by purchase or in any other transaction all or substantially all of the business
or property of, or stock or other ownership interests of, any Person, without
the prior written consent of the Purchaser; (6) change its jurisdiction of
organization, without the prior written consent of the Purchaser; nor (7) permit
any subsidiary of such Seller to do or to take any of the foregoing actions.

            (r) Each REIT Seller covenants and agrees that it shall at all times
continue to be (i) qualified as a real estate investment trust as defined in
Section 856 of the Code for so long as the Board of Directors deems it in the
best interests of the stockholders of such REIT Seller to remain so qualified
and (ii) entitled to a dividends paid deduction under Section 857 of the Code
with respect to dividends paid by it with respect to each taxable year for which
it claims a deduction on its Form 1120 - REIT filed with the United States
Internal Revenue Service for such year, or the entering into by any REIT Seller
of any material "prohibited transactions" as defined in Sections 857(b) and
856(c) of the Code. After the occurrence and during the continuation of any
monetary default or any default that results in the acceleration or required
prepayment of any indebtedness pursuant to the terms of this Agreement or any
other agreement between a Seller and Purchaser, no Seller shall make any payment
on account of, or set apart assets for, a sinking or other analogous fund for
the purchase, redemption, defeasance, retirement or other acquisition of any
equity or partnership interest of such Sellers, whether now or hereafter
outstanding, or make any other distribution in respect of any of the foregoing
or to any shareholder or equity owner of such Seller, either directly or
indirectly, whether in cash or property or in obligations of such Seller or any
of such Seller's consolidated Subsidiaries.


                                       35
<PAGE>

            Section 12. Periodic Due Diligence.

            (a) Each Seller acknowledges that Purchaser has the right to perform
continuing due diligence reviews with respect to the Mortgage Loans, for
purposes of verifying compliance with the representations, warranties and
specifications made hereunder, or otherwise, and each Seller agrees that upon
reasonable (but no less than one (1) Business Day's) prior notice to such
Seller, Purchaser or its authorized representatives will be permitted during
normal business hours to examine, inspect, and make copies and extracts of, the
Mortgage Files and any and all documents, records, agreements, instruments or
information relating to any Mortgage Loans in the possession or under the
control of Seller and/or the Custodian. Each Seller shall make available to
Purchaser a knowledgeable financial or accounting officer for the purpose of
answering questions respecting the Mortgage Loans. Without limiting the
generality of the foregoing, each Seller acknowledges that Purchaser may
purchase Mortgage Loans from such Seller based solely upon the information
provided by such Seller to Purchaser in the Closing Loan Purchase Detail or
Rewarehousing Loan Purchase Detail, as applicable, and the representations,
warranties and covenants contained herein, and that Purchaser, at its option,
has the right at any time to conduct a partial or complete due diligence review
on some or all of the Mortgage Loans purchased by Purchaser, including without
limitation ordering new credit reports and new appraisals on the related
Mortgaged Properties and otherwise re-generating the information used to
originate such Mortgage Loan. Purchaser may underwrite such Mortgage Loans
itself or engage a mutually agreed upon third party underwriter to perform such
underwriting. Each Seller agrees to cooperate with Purchaser and any third party
underwriter in connection with such underwriting, including, but not limited to,
providing Purchaser and any third party underwriter with access to any and all
documents, records, agreements, underwriting reports, instruments or information
relating to such Mortgage Loans in the possession, or under the control, of such
Seller. All such due diligence conducted in accordance with this Section 12
shall be at the expense of the related Seller.

            (b) Without limiting the generality of the foregoing, each Seller
acknowledges that upon demand by Purchaser, the related Seller shall deliver
within five Business Days copies of the Closing Instruction Letters reflecting
the addition of the Closing Instruction Letter Insert for all Wet Fundings and
Dry Fundings structured as Closing Transactions closed prior to the date of such
demand. Each Seller acknowledges Purchaser is authorized to contact any Escrow
Agent or any other person who has delivered a Closing Instruction Letter in
connection with any Wet Funding or Dry Funding in order to confirm the
information contained in such Closing Instruction Letter.

            Section 13. Third Party Servicing. If the Mortgage Loans are
serviced by a third party servicer (such third party servicer, the "Servicer"),
the related Seller (i) shall provide a copy of the servicing agreement to
Purchaser, which shall be in form and substance acceptable to Purchaser (the
"Servicing Agreement"); (ii) shall provide a Servicer Notice to the Servicer
substantially in the form of Exhibit W hereto; and (iii) hereby irrevocably
assigns to Purchaser and Purchaser's successors and assigns all right, title,
interest of such Seller in, to and under, and the benefits of, any Servicing
Agreement with respect to the Mortgage Loans. Any successor to the Servicer
shall be approved in writing by Purchaser prior to such successor's assumption
of servicing obligations with respect to the Mortgage Loans.


                                       36
<PAGE>

            Section 14. Confidentiality. Each Seller hereby acknowledges and
agrees that (i) all written or computer-readable information provided by
Purchaser to such Seller regarding Purchaser and (ii) the terms of this
Agreement (the "Purchaser Confidential Information"), shall be kept confidential
and each of their respective contents will not be divulged to any party without
Purchaser's consent except to the extent that (i) such Seller deems appropriate
to do so in working with legal counsel, auditors, taxing authorities or other
governmental agencies or regulatory bodies or in order to comply with any
applicable federal or state laws, (ii) any portion of Purchaser Confidential
Information is in the public domain other than due to a breach of this covenant,
(iii) such Seller deems appropriate in connection with exercising any or all of
Seller's rights or remedies or complying with any obligations under this
Agreement.

            Section 15. Term. This Agreement shall continue in effect until
terminated as to future transactions between the related Seller and Purchaser by
written instruction signed by either such Seller or Purchaser and delivered to
the other, provided that no termination will affect the obligations hereunder as
to any outstanding Transaction.

            Section 16. Exclusive Benefit of Parties; Assignment. This Agreement
is for the exclusive benefit of the parties hereto and their respective
successors and assigns and shall be deemed to give any legal or equitable right
to any other person, including the Custodian. Except as provided in Section 7,
no rights or obligations created by this Agreement may be assigned by any party
hereto without the prior written consent of the other parties.

            Section 17. Amendments; Waivers; Cumulative Rights. This Agreement
may be amended from time to time only by written agreement of the Sellers and
Purchaser. Any forbearance, failure or delay by such party in exercising any
right, power or remedy hereunder shall not be deemed to be a waiver thereof, and
any single or partial exercise by Purchaser of any right, power or remedy
hereunder shall not preclude the further exercise thereof. Every right, power
and remedy of Purchaser shall continue in full force and effect until
specifically waived by Purchaser in writing. No right, power or remedy shall be
exclusive, and each such right, power or remedy shall be cumulative and in
addition to any other right, power or remedy, whether conferred hereby or
hereafter available at law or in equity or by statute or otherwise.

            Section 18. Execution in Counterparts. This Agreement may be
executed in any number of counterparts, each of which shall be deemed an
original, but all of which shall constitute one and the same instrument.

            Section 19. Effect of Invalidity of Provisions. In case any one or
more of the provisions contained in this Agreement should be or become invalid,
illegal or unenforceable in any respect, the validity, legality and
enforceability of the remaining provisions contained herein or therein shall in
no way be affected, prejudiced or disturbed thereby.

            Section 20. GOVERNING LAW. THIS AGREEMENT SHALL BE GOVERNED BY AND
CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK WITHOUT REGARD TO
CONFLICT OF LAW RULES.

            Section 21. Notices. Any notices, consents, elections, directions
and other communications given under this Agreement shall be in writing and
shall be deemed to have


                                       37
<PAGE>

been duly given when telecopied or delivered by overnight courier to, personally
delivered to, or on the third day following the placing thereof in the mail,
first class postage prepaid to, the respective addresses set forth on the cover
page hereof for the Sellers and Purchaser, or to such other address as either
party shall give notice to the other parties pursuant to this Section 21.
Notices to Assignee shall be given to such address as Assignee shall provide to
the related Seller in writing.

            Section 22. Entire Agreement. This Agreement, the Funding
Confirmations and the Custodial Agreement contain the entire agreement among the
parties hereto with respect to the subject matter hereof, and supersede all
prior and contemporaneous agreements among them, oral or written, of any nature
whatsoever with respect to the subject matter hereof.

            Section 23. Costs of Enforcement. In addition to any other indemnity
specified in this Agreement, in the event of a breach by Seller of this
Agreement or the Custodial Agreement. Seller agrees to pay the reasonable
attorneys fees and expenses of Purchaser and, when applicable, Assignee incurred
in the enforcement of the Agreement as a consequence of such breach.

            Section 24. Purchaser's Appointment as Attorney-In-Fact(a) . Each
Seller hereby irrevocably constitutes and appoints Purchaser and any officer or
agent thereof, with full power of substitution, as its true and lawful
attorney-in-fact with full irrevocable power and authority in the place and
stead of such Seller and in the name of such Seller or in its own name, from
time to time in Purchaser's discretion, for the purpose of carrying out the
terms of this Agreement, to take any and all appropriate action and to execute
any and all documents and instruments which may be reasonably necessary or
desirable to accomplish the purposes of this Agreement, and, without limiting
the generality of the foregoing, such Seller hereby gives Purchaser the power
and right, on behalf of such Seller, without assent by, but with notice to, such
Seller, to do the following: in the name of such Seller, or in its own name, or
otherwise, to take possession of and endorse and collect any checks, drafts,
notes, acceptances or other instruments for the payment of moneys due under any
mortgage insurance or with respect to any other Mortgage Loans and to file any
claim or to take any other action or proceeding in any court of law or equity or
otherwise deemed appropriate by Purchaser for the purpose of collecting any and
all such moneys due under any such mortgage insurance or with respect to any
other Mortgage Loans whenever payable;

            (b) to pay or discharge taxes and liens levied or placed on or
threatened against the Mortgage Loans;

            (c) (A) to direct any party liable for any payment under any
Mortgage Loans to make payment of any and all moneys due or to become due
thereunder directly to Purchaser or as Purchaser shall direct; (B) to ask or
demand for, collect, receive payment of and receipt for, any and all moneys,
claims and other amounts due or to become due at any time in respect of or
arising out of any Mortgage Loans; (C) to sign and endorse any invoices,
assignments, verifications, notices and other documents in connection with any
Mortgage Loans; (D) to commence and prosecute any suits, actions or proceedings
at law or in equity in any court of competent jurisdiction to collect the
Mortgage Loans or any proceeds thereof and to enforce any other right in respect
of any Mortgage Loans; (E) to defend any suit, action or proceeding


                                       38
<PAGE>

brought against such Seller with respect to any Mortgage Loans; (F) to settle,
compromise or adjust any suit, action or proceeding described in clause (E)
above and, in connection therewith, to give such discharges or releases as
Purchaser may deem appropriate; and (G) generally, to sell, transfer, pledge and
make any agreement with respect to or otherwise deal with any Mortgage Loans as
fully and completely as though Purchaser were the absolute owner thereof for all
purposes, and to do, at Purchaser's option and such Seller's expense, at any
time, and from time to time, all acts and things which Purchaser deems necessary
to protect, preserve or realize upon the Mortgage Loans and Purchaser's liens
thereon and to effect the intent of this Agreement, all as fully and effectively
as such Seller might do;

            (d) to direct the actions of Custodian with respect to the Mortgage
Loans under the Custodial Agreement; and

            (e) to execute, from time to time, in connection with any sale
provided for in Section 7, any endorsements, assignments or other instruments of
conveyance or transfer with respect to the Mortgage Loans.

Each Seller hereby ratifies all that said attorneys shall lawfully do or cause
to be done by virtue hereof. This power of attorney is a power coupled with an
interest and shall be irrevocable.

The powers conferred on Purchaser hereunder are solely to protect Purchaser's
interests in the Mortgage Loans and shall not impose any duty upon it to
exercise any such powers. Purchaser shall be accountable only for amounts that
it actually receives as a result of the exercise of such powers, and neither it
nor any of its officers, directors, employees or agents shall be responsible to
any Seller for any act or failure to act hereunder, except for its or their own
gross negligence or willful misconduct.

            Section 25. Submission to Jurisdiction; Waivers.

            EACH SELLER HEREBY IRREVOCABLY AND UNCONDITIONALLY:

                        (1) SUBMITS FOR ITSELF AND ITS PROPERTY IN ANY LEGAL
                  ACTION OR PROCEEDING RELATING TO THIS REPURCHASE AGREEMENT AND
                  THE OTHER REPURCHASE DOCUMENTS, OR FOR RECOGNITION AND
                  ENFORCEMENT OF ANY JUDGMENT IN RESPECT THEREOF, TO THE
                  EXCLUSIVE GENERAL JURISDICTION OF THE COURTS OF THE STATE OF
                  NEW YORK, THE FEDERAL COURTS OF THE UNITED STATES OF AMERICA
                  FOR THE SOUTHERN DISTRICT OF NEW YORK, AND APPELLATE COURTS
                  FROM ANY THEREOF;

                        (2) CONSENTS THAT ANY SUCH ACTION OR PROCEEDING MAY BE
                  BROUGHT IN SUCH COURTS AND, TO THE EXTENT PERMITTED BY LAW,
                  WAIVES ANY OBJECTION THAT IT MAY NOW OR HEREAFTER HAVE TO THE
                  VENUE OF ANY SUCH ACTION OR PROCEEDING IN ANY SUCH COURT OR
                  THAT SUCH ACTION OR PROCEEDING


                                       39
<PAGE>

                  WAS BROUGHT IN AN INCONVENIENT COURT AND AGREES NOT TO PLEAD
                  OR CLAIM THE SAME;

                        (3) AGREES THAT SERVICE OF PROCESS IN ANY SUCH ACTION OR
                  PROCEEDING MAY BE EFFECTED BY MAILING A COPY THEREOF BY
                  REGISTERED OR CERTIFIED MAIL (OR ANY SUBSTANTIALLY SIMILAR
                  FORM OF MAIL), POSTAGE PREPAID, TO ITS ADDRESS SET FORTH ON
                  THE COVER PAGE HERETO OR AT SUCH OTHER ADDRESS OF WHICH
                  PURCHASER SHALL HAVE BEEN NOTIFIED;

                        (4) AGREES THAT NOTHING HEREIN SHALL AFFECT THE RIGHT TO
                  EFFECT SERVICE OF PROCESS IN ANY OTHER MANNER PERMITTED BY LAW
                  OR SHALL LIMIT THE RIGHT TO SUE IN ANY OTHER JURISDICTION; AND

                        (5) SELLER HEREBY IRREVOCABLY WAIVES, TO THE FULLEST
                  EXTENT PERMITTED BY APPLICABLE LAW, ANY AND ALL RIGHT TO TRIAL
                  BY JURY IN ANY LEGAL PROCEEDING ARISING OUT OF OR RELATING TO
                  THIS REPURCHASE AGREEMENT, ANY OTHER DOCUMENT RELATING THERETO
                  OR THE TRANSACTIONS CONTEMPLATED HEREBY OR THEREBY.

            Section 26. Construction. The headings in this Agreement are for
convenience only and are not intended to influence its construction. References
to Sections and Exhibits in this Agreement are to the Sections of and Exhibits
to this Agreement. The Exhibits and Schedules to this Agreement are part of this
Agreement, and are incorporated herein by reference. The singular includes the
plural, the plural the singular, and the words "and" and "or" are used in the
conjunctive or disjunctive as the sense and circumstances may require.


                                       40
<PAGE>

            Section 27. Effect of Amendment and Restatement. Upon the execution
of this Agreement by all parties hereto and the delivery of the opinion required
by Section 11(a)(ix), the Original Repurchase Agreement shall be amended,
restated and superseded in its entirety by this Agreement. The parties hereto
acknowledge and agree that (a) the liens and security interests granted under
the Original Repurchase Agreement are in full force and effect and, upon the
amendment and restatement of the Original Repurchase Agreement and the related
documents, such liens and security interests secure and continue to secure the
payment and performance of Seller's obligations under this Agreement and the
related documents, and (b) upon the effectiveness of such amendment and
restatement, all outstanding Mortgage Loans under, and as defined in, the
Original Repurchase Agreement, shall be deemed to be outstanding as Mortgage
Loans hereunder mutatis mutandis, in each case on the terms and conditions set
forth in this Agreement. Furthermore, the provisions of this Agreement shall
relate back to and shall govern all aspects of all sales of Mortgage Loans the
Sellers to the Purchaser beginning December 18, 2003 pursuant to the repurchase
facility.

                   [SIGNATURES COMMENCE ON FOLLOWING PAGE]


                                       41
<PAGE>

            IN WITNESS WHEREOF, Purchaser and the Sellers have duly executed
this Agreement as of the date and year set forth on the cover page hereof.

                                       UBS REAL ESTATE SECURITIES INC.


                                       By: /s/ George A. Mangiaracina
                                          --------------------------------------
                                          Name:  George A. Mangiaracina
                                          Title: Managing Director


                                       By: /s/ Robert Carpenter
                                          --------------------------------------
                                          Name:  Robert Carpenter
                                          Title: Director


                                       AMERICAN HOME MORTGAGE
                                         INVESTMENT CORP.


                                       By: /s/ Michael Strauss
                                          --------------------------------------
                                          Name:  Michael Strauss
                                          Title: President


                                       AMERICAN HOME MORTGAGE
                                         ACCEPTANCE, INC.


                                       By: /s/ Michael Strauss
                                          --------------------------------------
                                          Name:   Michael Strauss
                                          Title:  President


                                       AMERICAN HOME MORTGAGE
                                         HOLDINGS, INC.


                                       By:  /s/ Michael Strauss
                                          --------------------------------------
                                          Name:   Michael Strauss
                                          Title:  President

<PAGE>

                                       AMERICAN HOME MORTGAGE CORP.


                                       By: /s/ Michael Strauss
                                          --------------------------------------
                                          Name:   Michael Strauss
                                          Title:  President


                                       COLUMBIA NATIONAL, INCORPORATED


                                       By:   /s/ Michael Strauss
                                          --------------------------------------
                                          Name:   Michael Strauss
                                          Title:  President

Source: OneCLE Business Contracts.