<PAGE>

                                                                   EXHIBIT 10.15

                            ASSIGNMENT AND ASSUMPTION

                                    AGREEMENT

      This ASSIGNMENT AND ASSUMPTION AGREEMENT (the "Agreement") is made and
entered into as of this 1st day of July, 2003 (the "Effective Date") by and
between ARBOR COMMERCIAL MORTGAGE LLC (the "Assignor"), and Arbor Realty Limited
Partnership (the "Assignee").

      WHEREAS, the. Assignor and Nomura Credit & Capital, Inc. (the "Buyer")
have entered into a Master Repurchase Agreement dated as of November 18, 2002,
as amended as of July 1, 2003 (the "Repurchase Agreement") between the Assignor
and the Buyer.

      WHEREAS, the Repurchase Agreement permits the Assignor to assign its
rights and obligations under the Repurchase Agreement as provided thereunder;

      WHEREAS, the Assignor, the Buyer and U.S. Bank National Association (the
"Custodian") have entered into a Custodial Agreement dated as of November 18,
2002 (the "Custodial Agreement") for the custody, administration and servicing
of Loans underlying Purchased Assets;

      WHEREAS, Section 7.7 of the Custodial Agreement permits the Assignor to
assign its rights and obligations under the Custodial Agreement with the prior
written consent of the other parties thereto; and

      WHEREAS, on or prior to the Effective Date, the Assignor will contribute
to the Assignee the portfolio of Loans listed in Schedule 1 hereto, which Loans
have an aggregate principal balance of $86,603,234.00 on the Effective Date (the
"Contributed Loans") and, (ii) the Assignor will assign to the Assignee all its
rights and obligations under the Repurchase Agreement, the Custodial Agreement
and the other Program Documents (other than its rights and obligations to act as
Servicer for the Loans), and the Assignee has agreed to accept the pledge,
assignment and transfer of the foregoing.

      NOW, THEREFORE, in consideration of the mutual covenants and agreements
contained herein, and for other good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged, the parties hereto agree as
follows:

      Capitalized terms used and not otherwise defined herein shall have the
meaning assigned thereto in the Repurchase Agreement or the Custodial Agreement,
as applicable.

      Section 1. AGREEMENTS

      1.    Contribution, Assignment and Agreements. On or prior to the
            Effective Date, the Assignor shall contribute to the Assignee the
            Contributed Loans, and the Assignor shall assign to the Assignee all
            of its respective rights,
<PAGE>
            privileges, and any other interests, and obligations, as Seller
            under the Repurchase Agreement, the Custodial Agreement and the
            other Program Documents; provided that (subject to the second
            proviso below) the Assignor shall not assign to the Assignee any
            interest in the loan on the Professional Tower (an office building
            located in Miami, Florida) (the "Tower Loan"), which Tower Loan has
            an outstanding principal balance of $10,584,492 on the Effective
            Date, and is collateralized by a $8,800,000 Bridge Loan and a
            $1,784,792 Mezzanine Loan; and provided further that the Repurchase
            Agreement shall be deemed to remain in effect with respect to the
            Tower Loan from the Effective Date through the date on which the
            repurchase transactions contemplated by the letter agreement dated
            July 1, 2003 (the "Letter Agreement") by the Assignor, the Assignee
            and certain of their Affiliates are consummated. So long as any
            Purchased Asset shall remain subject to the Repurchase Agreement,
            the Assignor shall continue to act as Servicer with respect to the
            Loans underlying such Purchased Asset for the benefit of Buyer
            pursuant to and in accordance with the terms of the Custodial
            Agreement, the Repurchase Agreement and the other Program Documents.
            Following the repurchase of a Purchased Asset by the Assignee from
            the Buyer on or after the Effective Date, and the termination of the
            Repurchase Agreement with respect to such Purchased Asset, the
            Servicer shall continue to act as Servicer with respect to the Loans
            underlying such Purchased Asset, pursuant to and in accordance with
            the terms of the Custodial Agreement. To the extent of any
            inconsistency between the Custodial Agreement and the Services
            Agreement dated as of July 1, 2003 among Arbor Realty Trust, Inc.,
            the Assignee and the Assignor, the terms of the Custodial Agreement
            shall govern the servicing of Loans by the Assignor. The Buyer and
            the Custodian hereby consent to such assignment.

      2.    Purchased Assets. The Assignor hereby agrees to take all action
            necessary to amend any existing, or file any new, Uniform Commercial
            Code financing statements, necessary to maintain the first priority
            security interest of the Buyer to and in the Collateral. On and as
            of the Effective Date, the Assignee shall assume liability for any
            payment or other obligations under the Repurchase Agreement and the
            other Program Documents, including but not limited to, its
            obligations relating to Margin Calls, repurchase of Purchased
            Assets, and the payment of the expenses of the Custodian, and the
            Assignor, in its capacity as Servicer for the Loans. In addition, on
            and as of the Effective Date, the Assignee shall become entitled to
            any Income pursuant to, and as permitted by, the Repurchase
            Agreement and the other Program Documents.

      3.    Assumption. The Assignee hereby accepts the foregoing assignment,
            and hereby assumes and agrees to pay, perform or otherwise provide
            for any and all duties and obligations of the Assignor, as Seller,
            under and in accordance with the terms of the Repurchase Agreement,
            the Custodial Agreement and the other Program Documents.
<PAGE>
      4.    Further Assurances and Agreements. The Assignor and the Assignee
            further agree that, upon the reasonable request of the other or the
            Buyer, each will execute, acknowledge and deliver all such
            additional documents and instruments as may be reasonably necessary
            to carry out the purposes of this Agreement.

            The Assignor and the Assignee further understand and agree that the
            Events of Default set forth in Sections 18(q) and (r) of the
            Repurchase Agreement relating to change in Control and net worth
            have been amended as of July 1, 2003, pursuant to and as provided by
            Amendment No. One to the Repurchase Agreement.

      Section 2. REPRESENTATIONS AND WARRANTIES

      Each of the Assignor and the Assignee represents as of the Effective Date
as follows:

      1.    The Assignor and the Assignee each represents and warrants that the
            agreement attached hereto as Exhibit A is a true and accurate copy
            of the Repurchase Agreement. The Assignor represents and warrants
            that the Repurchase Agreement is in full force and effect as of the
            date hereof and the provisions of such Repurchase Agreement have not
            been waived, amended or modified (other than as therein provided),
            nor have notices of termination been given thereunder.

      2.    The Assignor and the Assignee each represents and warrants that the
            agreement attached hereto as Exhibit B is a true and accurate copy
            of the Custodial Agreement. The Assignor represents and warrants
            that the Custodial Agreement is in full force and effect as of the
            date hereof and the provisions of such Custodial Agreement have not
            been waived, amended or modified (other than as therein provided),
            nor have notices of termination been given thereunder.

      3.    Arbor Commercial Mortgage LLC, as Servicer, and the Assignee, as
            Seller pursuant to the Repurchase Agreement jointly and severally
            make, to the Buyer, Agent and each subsequent purchaser of the
            Loans, the representations and warranties set forth in Appendix A to
            the Custodial Agreement, and shall continue to make such
            representations as required under the Repurchase Agreement, the
            Custodial Agreement and the other Program Documents.

      The Assignor further warrants and represents to, and covenants with, the
Assignee as of the date hereof as follows:

      1.    The Assignor is duly organized, validly existing and in good
            standing under the laws of the jurisdiction of its formation;
<PAGE>
      2.    The Assignor has full power and authority to execute, deliver and
            perform its obligations under this Agreement, and to consummate the
            transactions set forth herein. The consummation of the transactions
            contemplated by this Agreement is in the ordinary course of the
            Assignor's business and will not conflict with, or result in a
            breach of, any of the terms, conditions or provisions of the
            Assignor's certificate of formation or operating agreement or any
            legal restriction, or any material agreement or instrument to which
            the Assignor is now a party or by which it is bound, or result in
            the violation of any law, rule, regulation, order, judgment or
            decree to which the Assignor or its property is subject. The
            execution, delivery and performance by the Assignor of this
            Agreement and the consummation by it of the transactions
            contemplated hereby, have been duly authorized by all necessary
            action on the part of the Assignor. This Agreement has been duly
            executed and delivered by the Assignor and, upon the due
            authorization, execution and delivery by the Assignor and the
            Assignee, will constitute the valid and legally binding obligation
            of the Assignor enforceable against the Assignor in accordance with
            its terms except as enforceability may be limited by bankruptcy,
            reorganization, insolvency, moratorium or other similar laws now or
            hereafter in effect relating to creditors' rights generally, and by
            general principles of equity regardless of whether enforceability is
            considered in a proceeding in equity or at law;

      3.    No material consent, approval, order or authorization of, or
            declaration, filing or registration with, any governmental entity is
            required to be obtained or made by the Assignor in connection with
            the execution, delivery or performance by the Assignor of this
            Agreement, or the consummation by it of the transactions
            contemplated hereby; and

      4.    There is no action, suit, proceeding, investigation or litigation
            pending or, to the Assignor's knowledge, threatened, which either in
            any instance or in the aggregate, if determined adversely to the
            Assignor, would adversely affect the Assignor's execution or
            delivery of, or the enforceability of, this Agreement, or the
            Assignor's ability to perform its obligation under this Agreement.

      The Assignee further warrants and represents to, and covenants with, the
Assignor as of the date hereof as follows:

      1.    The Assignee is a limited partnership duly organized, validly
            existing and in good standing under the laws of the jurisdiction of
            its formation and has all requisite power and authority to acquire,
            own, sell, repurchase and otherwise dispose of Purchased Assets;

      2.    The Assignee has full power and authority to execute, deliver and
            perform its obligations under this Agreement, and to consummate the
            transactions set forth herein. The consummation of the transactions
            contemplated by
<PAGE>
            this Agreement is in the ordinary course of the Assignee's business
            and will not conflict with, or result in a breach of, any of the
            terms, conditions or provisions of the Assignee's limited
            partnership agreement or any legal restriction, or any material
            agreement or instrument to which the Assignee is now a party or by
            which it is bound, or result in the violation of any law, rule,
            regulation, order, judgment or decree to which the Assignee or its
            property is subject. The execution, delivery and performance by the
            Assignee of this Agreement and the consummation by it of the
            transactions contemplated hereby, have been duly authorized by all
            necessary limited partnership action on the part of the Assignee.
            This Agreement has been duly executed and delivered by the Assignee
            and, upon the due authorization, execution and delivery by the
            Assignor and the Assignee, will constitute the valid and legally
            binding obligation of the Assignee enforceable against the Assignee
            in accordance with its terms except as enforceability may be limited
            by bankruptcy, reorganization, insolvency, moratorium or other
            similar laws now or hereafter in effect relating to creditors'
            rights generally, and by general principles of equity regardless of
            whether enforceability is considered in a proceeding in equity or at
            law;

      3.    No material consent, approval, order or authorization of, or
            declaration, filing or registration with, any governmental entity is
            required to be obtained or made by the Assignee in connection with
            the execution, delivery or performance by the Assignee of this
            Agreement, or the consummation by it of the transactions
            contemplated hereby;

      4.    There is no action, suit, proceeding, investigation or litigation
            pending or, to the Assignee's knowledge, threatened, which either in
            any instance or in the aggregate, if determined adversely to the
            Assignee, would adversely affect the Assignee's execution or
            delivery of, or the enforceability of, this Agreement, or the
            Assignee's ability to perform its obligation under this Agreement;

      5.    The Assignee agrees to be bound by all of the terms, covenants and
            conditions of the Repurchase Agreement, the Custodial Agreement and
            the other Program Documents;

      6.    The Assignee is solvent and will not be rendered insolvent by the
            transactions contemplated by this Agreement and after giving effect
            to such transactions, the Assignee will not be left with an
            unreasonably small amount of capital with which to engage in its
            business; and

      7.    The Assignee is not required to be registered as an "investment
            company" as defined under the Investment Company Act nor as an
            entity under the control of an "investment company" as defined under
            the Investment Company Act.
<PAGE>
      Section 3. CONDITIONS PRECEDENT

      As conditions precedent to the execution and delivery of this Agreement
and the issuance by the Buyer of its written consent to the assignment by the
Assignor of all its rights and obligations as Seller under the Repurchase
Agreement to the Assignee, the Buyer shall have received, in form satisfactory
to the Buyer:

      1.    This Agreement, duly authorized and executed by the Assignor, the
            Assignee and the Custodian;

      2.    Evidence that all other actions necessary or, in the opinion of the
            Buyer, desirable to perfect and protect the Buyer's interest in the
            Purchased Assets and other Collateral have been taken, including,
            without limitation, the filing of new, or the amendment of existing,
            Uniform Commercial Code financing statements on Form UCC-1 or other
            applicable Form;

      3.    Written confirmation by the Assignee, which shall be accompanied by
            a certificate of an authorized officer of the Assignor that (i) the
            Assignor has made, and the Assignee has received, the Contributed
            Loans, (ii) the offering described in that Preliminary Offering
            Memorandum dated June 27, 2003 with respect to the stock offering by
            Arbor Realty Trust, Inc. has been completed, and that a portion of
            the proceeds thereof has been contributed by Arbor Realty Trust,
            Inc. in cash to the Assignee, and that such cash contribution has
            been deposited in that certain bank account no. 7424022551 at North
            Fork Bank and (iii) any other related required payments under
            paragraphs (i) and (ii) above have been made and received by the
            appropriate parties;

      4.    An opinion of Cullen and Dykman, counsel to the Assignee, as to the
            transactions contemplated by this Agreement, in a form satisfactory
            to the Buyer;

      5.    A certified copy of the Assignee's limited partnership resolutions
            approving this Agreement and the Program Documents and Transactions
            thereunder (either specifically or by general resolution), and all
            documents evidencing other necessary limited partnership action or
            governmental approvals as may be required in connection with this
            Agreement and the Program Documents;

      6.    An incumbency certificate of the Seller's general partner certifying
            the names, true signatures and titles of the Seller's
            representatives duly authorized to request Transactions hereunder
            and to execute this Agreement and the Program Documents, as
            applicable, and the other documents to be delivered hereunder;

      7.    No Default or Event of Default shall have occurred, both immediately
            before and after the execution and delivery of this Agreement and
            the Program Documents by the Assignor and/or the Assignee, as
            applicable;
<PAGE>
      8.    Arbor Realty Trust, Inc. shall have issued a Guaranty in the form
            attached hereto as Exhibit A to guarantee the Obligations of the
            Assignee under the Repurchase Agreement and any other obligations of
            the Assignee under this Agreement; and

      9.    As of the close of business on the Effective Date, the Assignee
            shall have a new worth of at least $140 million.

      Section 4. COUNTERPARTS

      This Agreement may be executed in one or more counterparts, each of which
shall be deemed an original, and all of which, taken together, shall constitute
one and the same instrument, which may be sufficiently evidenced by one
counterpart.

      Section 5. SUCCESSORS AND ASSIGNS

      This Agreement shall be binding upon and inure to the benefit of the
parties hereto and their successors and permitted assignees.

      Section 6. APPLICABLE LAW

      This Agreement shall be governed by, interpreted under and construed in
accordance with the laws of the state of New York, without regard to the
conflicts of law principles thereof.

                            (Signature Page Follows)
<PAGE>
      IN WITNESS WHEREOF, the Assignor and the Assignee have executed and
delivered this Agreement as of the day and year first above written.

                                    ARBOR COMMERCIAL MORTGAGE LLC

                                    By:     /s/ John Natalone
                                            -------------------------------
                                    Name:   John Natalone
                                            -------------------------------
                                    Title:  Vice President, Treasurer
                                            -------------------------------


                                    ARBOR REALTY LIMITED

                                    PARTNERSHIP

                                    By:     /s/ Frederick C. Herbst
                                            -------------------------------
                                    Name:   Frederick C. Herbst
                                            -------------------------------
                                    Title:  Chief Financial Officer
                                            -------------------------------

Acknowledged and Agreed:

                                    NOMURA CREDIT & CAPITAL, INC.


                                    By:     /s/ James K. Lieblich
                                            -------------------------------
                                    Name:   James K. Lieblich
                                            -------------------------------
                                    Title:  President
                                            -------------------------------

                                    U.S. BANK NATIONAL ASSOCIATION

                                    By:     /s/ Charles F. Pedersen
                                            -------------------------------
                                    Name:   Charles F. Pedersen
                                            -------------------------------
                                    Title:  Vice President
                                            -------------------------------


                                      S-1
<PAGE>
                                   Schedule 1

                             List of Assigned Loans

NOMURA ASSETS TRANSFERRING TO ART

<TABLE>
<CAPTION>
PROPERTY               TYPE                     UPB            AMOUNT FINANCED
--------               ----                     ---            ---------------
<S>                    <C>                    <C>              <C>
CDS-Portfolio          Mezz                    $4,991,001.00       $3,743,250.75
Schron                 Mezz                   $10,800,000.00       $8,468,177.40
Scron II               Mezz                    $8,500,000.00       $6,664,769.25
Grand Plaza            Bridge                 $25,382,233.00      $20,281,974.40
Tropical Gardens       Bridge                  $8,800,000.00       $7,040,000.00
Dylan Hotel            Bridge                 $14,000,000.00      $11,900,000.00
Concord & Henry        Bridge                  $5,000,000.00       $4,000,000.00
Palmetto Village       Bridge                  $9,130,000.00       $7,304,000.00

TOTAL                                         $86,603,234.00      $69,402,171.80
</TABLE>