<PAGE>

                                                                 Exhibit 10.27.3


                              EIGHTH AMENDMENT TO
                              AMENDED AND RESTATED
                      MORTGAGE LOAN WAREHOUSING AGREEMENT
                      -----------------------------------


  EIGHTH AMENDMENT TO AMENDED AND RESTATED MORTGAGE LOAN WAREHOUSING AGREEMENT
(the "Amendment"), dated as of May 31, 2001 by and among AMERICAN HOME
MORTGAGE CORP. ("American Home"), MARINA MORTGAGE COMPANY, INC. ("Marina" and,
together with American Home, the "Companies" and each a "Company"), AMERICAN
HOME MORTGAGE HOLDINGS, INC. ("Guarantor"), FIRST UNION NATIONAL BANK, COMERICA
BANK, BANKERS TRUST COMPANY and THE CHASE MANHATTAN BANK ("Chase")
(collectively, the "Lenders") and FIRST UNION NATIONAL BANK, as administrative
agent for the Lenders (in such capacity, the "Administrative Agent").

                             STATEMENT OF PURPOSE
                             --------------------

  WHEREAS, the Companies, the Lenders (other than Chase), and the Administrative
Agent are parties to an Amended and Restated Mortgage Loan Warehousing Agreement
dated as of May 25, 2000, as amended by a First Amendment to Amended and
Restated Mortgage Loan Warehousing Agreement dated as of August 15, 2000, by a
Second Amendment to Amended and Restated Mortgage Loan Warehousing Agreement
dated as of August 30, 2000, by a Third Amendment to Amended and Restated
Mortgage Loan Warehousing Agreement dated as of September 28, 2000, by a Fourth
Amendment to Amended and Restated Mortgage Loan Warehousing Agreement dated as
of November 10, 2000, by a Fifth Amendment to Amended and Restated Mortgage Loan
Warehousing Agreement dated as of December 6, 2000, by a Sixth Amendment to
Amended and Restated Mortgage Loan Warehousing Agreement dated as of May 1,
2001, and by a Seventh Amendment to Amended and Restated Mortgage Loan
Warehousing Agreement dated as of May 15, 2001 (as so amended, the "Credit
Agreement"); and

  WHEREAS, Chase desires to become a party to and a Lender under the Credit
Agreement and all other instruments, agreements and documents entered into in
connection therewith pursuant to the terms of Paragraph 10(j) of the Credit
Agreement; and

  WHEREAS, the parties hereto wish to amend the Credit Agreement to provide for
the inclusion of Chase as a party thereto and a Lender thereunder and as more
specifically set forth below; and

  WHEREAS, subject to and upon the terms and conditions herein set forth, the
Lenders and the Administrative Agent are willing to continue to make available
to the Companies the credit facilities provided for in the Credit Agreement; and

  WHEREAS, a specific condition to the willingness of the Lenders and the
Administrative Agent to continue to make available to the Companies the credit
facilities provided for in the Credit Agreement is the reaffirmation by  the
Guarantor of the Guaranty to which the Guarantor is a party; and
<PAGE>

  WHEREAS, the Guarantor will derive a material benefit from the continued
availability to the Companies of the credit facilities provided for in the
Credit Agreement and therefore the Guarantor is willing to reaffirm the Guaranty
to which the Guarantor is a party;

  NOW, THEREFORE, in consideration of the premises and agreements contained
herein, and for good and valuable consideration, the receipt and sufficiency of
which are acknowledged by the parties hereto, the parties hereto hereby agree as
follows:

  1.  All capitalized terms used herein and not otherwise defined shall have the
respective meanings provided to such terms in the Credit Agreement, as amended
hereby.

  2.  Amendments to the Credit Agreement.
      ----------------------------------

      a.   The Credit Agreement is hereby amended to include, as a party
thereto, Chase, and the team "Lenders" as defined in the introductory paragraph
to, and Paragraph 11 of, the Credit Agreement is hereby amended to include
Chase, and as of the date hereof, Chase shall be deemed to be a "Lender" under
the Credit Agreement and under each instrument, agreement and document entered
into in connection therewith.

      b.   Schedule I and Schedule III to the Credit Agreement are hereby
           ----------     ------------
deleted in their entireties and the forms of Schedule I and Schedule III
                                             ----------     ------------
attached to this Amendment as Annex I and Annex II, respectively, are hereby
substituted in lieu thereof.

  3.  This Amendment shall become effective as of the date hereof, provided that
the Administrative Agent shall have received by such date the following items:

      a.   A copy of this Amendment executed by the Companies, the Guarantor,
     each of the Lenders and the Administrative Agent (whether such parties
     shall have signed the same or different copies);

      b.  A Promissory Note of even date herewith, as duly executed by each of
     the Companies, such note to be payable by the Companies to the order of
     Chase and to be in the form attached as Annex III hereto (such note to be
     considered a Note for all purposes);

      c.  A Reaffirmation of Guaranty of even date herewith in form and
     substance satisfactory to the Administrative Agent, executed by the
     Guarantor;

      d.  Certificates of even date herewith signed by the President or any Vice
     President of each of the Companies and of the Guarantor and attested to by
     the Secretary or any Assistant Secretary of each of the Companies and of
     the Guarantor certifying that (i) the Articles, Bylaws and resolutions of
     such Company or of the Guarantor, as applicable, previously delivered to
     the Administrative Agent remain in full force and effect except as provided
     therein, (ii) such Company or the Guarantor, as applicable, remains in good
     standing, (iii) all representations and warranties of such Company or the
     Guarantor, as

                                       2
<PAGE>

     applicable, previously made to the Administrative Agent and the Lenders
     remain true, complete and accurate, and (iv) no Event of Default or
     Potential Default has occurred and is continuing;

              e.   Resolutions of each of the Companies and of the Guarantor
     authorizing the execution of this Amendment and, with respect to the
     Guarantor, the Reaffirmation of Guaranty, and, with respect to the
     Companies, the note listed in subsection (b) above; and

              f.   A facility fee, payable to the Administrative Agent for the
     benefit of Chase, in the amount and as further provided in Paragraph
     2(l)(7) of the Credit Agreement.

     4.  This Amendment is limited and, except as set forth herein, shall not
constitute a modification, acceptance or waiver of any other provision of the
Credit Agreement, or any other document or instrument entered into in connection
therewith.

     5.  This Amendment may be executed in any number of counterparts by the
different parties hereto on separate counterparts, each of which counterparts
when executed and delivered shall be an original, but all of which together
shall constitute one and the same instrument.  A complete set of counterparts
shall be lodged with the Companies and the Administrative Agent.

     6.  This Amendment and the rights and obligations of the parties hereunder
shall be construed in accordance with and governed by the laws of the State of
North Carolina.

     7.  From and after the date hereof, all references in the Credit Agreement,
and any other document or instrument entered into in connection therewith, to
the Credit Agreement shall be deemed to be references to the Credit Agreement as
amended hereby.  Chase hereby assumes, and agrees to be bound from and after the
date hereof under and by, the terms of the Credit Agreement and all instruments,
agreements and documents entered into in connection therewith.  Chase shall be
considered to be a "Lender" for all purposes under the Security Agreement, the
Uniform Commercial Code financing statements filed pursuant thereto, the
Guaranty and the other Credit Documents.

     8.  The Guarantor joins in the execution and delivery of this Amendment to
acknowledge and consent to the terms hereof and hereby reaffirms its obligations
under the Guaranty (as reaffirmed by the Reaffirmation of Guaranty) and agrees
that the Guaranty (as reaffirmed by the Reaffirmation of Guaranty) shall remain
in full force and effect with respect to the Obligations.

     9.  EACH OF THE LENDERS, THE ADMINISTRATIVE AGENT, THE GUARANTOR AND EACH
OF THE COMPANIES HEREBY KNOWINGLY, VOLUNTARILY AND INTENTIONALLY WAIVES, TO THE
FULLEST EXTENT PERMITTED BY LAW, THE RIGHT ANY OF THEM MAY HAVE TO A TRIAL BY
JURY IN RESPECT OF ANY LITIGATION BASED HEREON, OR ARISING OUT OF, UNDER OR IN
CONNECTION WITH THIS AMENDMENT AND ANY AGREEMENT

                                       3
<PAGE>

CONTEMPLATED TO BE EXECUTED IN CONJUNCTION HEREWITH, OR ANY COURSE OF CONDUCT,
COURSE OF DEALING, STATEMENTS (WHETHER VERBAL OR WRITTEN) OR ACTIONS OF ANY
PARTY RELATING HERETO OR THERETO. THIS PROVISION IS A MATERIAL INDUCEMENT FOR
THE LENDERS AND THE ADMINISTRATIVE AGENT TO ENTER INTO THIS AMENDMENT.

                 [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK]


                                       4
<PAGE>

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed
             and sealed as of the day and year first above written.


                              AMERICAN HOME MORTGAGE CORP., a
                              New York corporation



                              By /s/ Richard Silver
                                 --------------------------
                              Name Richard Silver
                                   ------------------------
                              Title Controller
                                    -----------------------


                              MARINA MORTGAGE COMPANY, INC., a
                              California corporation



                              By /s/ Richard Silver
                                 --------------------------
                              Name Richard Silver
                                   ------------------------
                              Title Controller
                                    -----------------------


ACKNOWLEGED AND AGREED TO:

                              AMERICAN HOME MORTGAGE HOLDINGS, INC., a Delaware
                              corporation, as Guarantor



                              By /s/ Richard Silver
                                 --------------------------
                              Name Richard Silver
                                   ------------------------
                              Title Controller
                                    -----------------------

                                       5
<PAGE>

                              FIRST UNION NATIONAL BANK, a national banking
                              association, as Administrative Agent and a Lender


                              By /s/ Anthony J. Alfieri
                                 ------------------------------
                              Name Anthony J. Alfieri
                                   ----------------------------
                              Title Vice President
                                    ---------------------------

                              COMERICA BANK, a
                              Michigan banking corporation, as a Lender


                              By /s/ Heather Hogle
                                 ------------------------------
                              Name Heather Hogle
                                   ----------------------------
                              Title Account Officer
                                    ---------------------------


                              BANKERS TRUST COMPANY, a New York banking
                              corporation, as a Lender


                              By /s/ Glenn Minkoff
                                 ------------------------------
                              Name Glenn Minkoff
                                   ----------------------------
                              Title Director
                                    ---------------------------

                              THE CHASE MANHATTAN BANK, a New York banking
                              corporation, as a Lender


                              By /s/ Robert A. Salcetti
                                 ------------------------------
                              Name Robert A. Salcetti
                                   ----------------------------
                              Title Managing Director
                                    ---------------------------

                                       6
<PAGE>

                                                                         ANNEX I

                                  SCHEDULE I
                                      TO
           AMENDED AND RESTATED AMENDED AND RESTATED MORTGAGE LOAN
                             WAREHOUSING AGREEMENT
                           DATED AS OF May 25, 2000
                  BY AND AMONG AMERICAN HOME MORTGAGE CORP.,
                        MARINA MORTGAGE COMPANY, INC.,
                  FIRST UNION NATIONAL BANK AS ADMINISTRATIVE
                      AGENT AND THE LENDERS PARTY THERETO

                             Schedule of Addresses
                             ---------------------


COMPANIES:

American Home Mortgage Corp.
520 Broadhollow Road
Melville, New York  11747
Attention:__________________________

Marina Mortgage Company, Inc.,
520 Broadhollow Road
Melville, New York  11747
Attention:__________________________

GUARANTOR:

American Home Mortgage Holdings, Inc.
520 Broadhollow Road
Melville, New York  11747
Attention:__________________________

ADMINISTRATIVE AGENT:

First Union National Bank
One First Union Center, TW-09
301 South College Street, 9th Floor
Charlotte, North Carolina  28288-0610
Attention:  Anthony J. Alfieri

                                       7
<PAGE>

LENDERS:

First Union National Bank
One First Union Center, TW-09
301  South College Street, 9th Floor
Charlotte, North Carolina 28288-0610
Attention:  Anthony J. Alfieri

Comerica Bank
One Detroit Center
500 Woodward Avenue, 7th Floor
Detroit, Michigan  48226
Attention:  Heather D. Hogle

Bankers Trust Company
Financial Institutions Group
25th floor
New York, New York  10006
Attention:  Glenn Minkoff

The Chase Manhattan Bank
707 Travis Street
Corporate Mortgage Finance, 6th Floor North
Houston, Texas  77002
Attention:  Cynthia Crites

                                       8
<PAGE>

                                                                        ANNEX II

                                 SCHEDULE III
                                      TO
           AMENDED AND RESTATED AMENDED AND RESTATED MORTGAGE LOAN
                             WAREHOUSING AGREEMENT
                           DATED AS OF May 25, 2000
                   BY AND AMONG AMERICAN HOME MORTGAGE CORP.,
                        MARINA MORTGAGE COMPANY, INC.,
                  FIRST UNION NATIONAL BANK AS ADMINISTRATIVE
                      AGENT AND THE LENDERS PARTY THERETO

                              Commitment Schedule
                              -------------------

<TABLE>
<CAPTION>
            Lender                    Maximum Commitment                 Percentage Share
            ------                    ------------------                 ----------------
<S>                                   <C>                                 <C>

First Union National Bank               $ 50,000,000                            43.48%

Bankers Trust Company                   $ 25,000,000                            21.74%

The Chase Manhattan Bank                $ 25,000,000                            21.74%

Comerica Bank                           $ 15,000,000                            13.04%

AGGREGATE FACILITY COMMITMENT           $115,000,000                           100.00%
</TABLE>

                                       9
<PAGE>

                                                                       ANNEX III


                           FORM OF PROMISSORY NOTE
                           -----------------------

                                                        _________________,2001


  FOR VALUE RECEIVED, AMERICAN HOME MORTGAGE CORP., a New York corporation
("American Home") and MARINA MORTGAGE COMPANY, INC., a California corporation
("Marina" and, together with American Home, the "Companies") hereby
unconditionally promise, jointly and severally, to pay to the order of THE CHASE
MANHATTAN BANK, a __________________________ (the "Lender"), at the office of
FIRST UNION NATIONAL BANK, a national banking association (the "Administrative
Agent"), at its office located at One First Union Center, TW-09, 301 South
College Street, Charlotte, North Carolina 28288-0610, in lawful money of the
United States and in immediately available funds, on the dates required under
that certain Amended and Restated Mortgage Loan Warehousing Agreement dated as
of May 25, 2000 by and among the Companies, the lenders from time to time
parties thereto, including the Lender, and the Administrative Agent (as the same
has been and may be further amended, extended, restated, modified, renewed or
replaced from time to time, the "Agreement" and with the capitalized terms not
otherwise defined herein used with the meanings given such terms in the
Agreement), the principal amount of Lender's Regular Repayment Share of each
Regular Loan made under the Agreement.

  The Companies further agree, jointly and severally, to pay interest in like
money and funds at the office of the Administrative Agent referred to above, on
the unpaid principal balance hereof from the date advanced until paid in full on
the dates and at the applicable rates set forth in the Agreement.  The holder of
this Note is hereby authorized to record the date and amount of Lender's
Percentage Share and Regular Repayment Share of each Regular Loan, the date and
amount of each payment of principal and interest, and applicable interest rates
and other information with respect thereto, on the schedules annexed to and
constituting a part of this Note (or by any analogous method the holder hereof
may elect consistent with its customary practices) and any such recordation
shall, absent manifest error, constitute prima facie evidence of the accuracy of
                                         ----- -----
the information so recorded; provided, however, that the failure to make a
notation or the inaccuracy of any notation shall not limit or otherwise affect
the obligations of the Companies under the Credit Documents.

  The Companies waive presentment, demand, protest, notice of dishonor, notice
of demand or intent to demand, notice of acceleration or intent to accelerate,
and all other notices, and agree that no extension or indulgence to the
Companies (or either of them) or release, substitution or nonenforcement of any
security, or release or substitution of any of the Companies, any guarantor or
any other party, whether with or without notice, shall affect the obligations of
any of the Companies.

  This Note is one of the Notes referred to in, and is entitled to all the
benefits of, the Agreement.  Reference is hereby made to the Agreement and to
the Security Agreement for rights and obligations of payment and prepayment,
collateral security, Events of Default and the rights of acceleration of the
maturity hereof upon the occurrence of an Event of Default.

                                       10
<PAGE>

  This Note shall be governed by, and construed in accordance with, the laws of
the State of North Carolina, and is being executed by the duly authorized
officers of each of the Companies as of the day and year first above written.

                                          AMERICAN HOME MORTGAGE CORP.,
                                          a New York corporation
[CORPORATE SEAL]

Attest:

By:_______________________                By:________________________
Name:_____________________                Name:______________________
Title:____________________                Title:_____________________


                                          MARINA MORTGAGE COMPANY, INC.,
                                          a California corporation
[CORPORATE SEAL]

Attest:

By:_______________________                By:________________________
Name:_____________________                Name:______________________
Title:____________________                Title:_____________________

                                       11