Exhibit 10.5


                                VOTING AGREEMENT

      This VOTING AGREEMENT ("Agreement") is entered into as of October 1, 2006
by and among FSP 50 SOUTH TENTH STREET CORP., a Delaware corporation ("50 South
Tenth Street"), GEORGE J. CARTER, an individual resident of the Commonwealth of
Massachusetts ("GJC"), and FRANKLIN STREET PROPERTIES CORP., a Maryland
corporation ("FSP").

      WHEREAS, 50 South Tenth Street is currently governed by that certain
Amended and Restated Certificate of Incorporation dated September 12, 2006 and
filed with the Delaware Department of State on September 15, 2006 (the
"Charter");

      WHEREAS, 50 South Tenth Street issued one (1) share of common stock, $0.01
par value per share (the "Common Stock");

      WHEREAS, FSP owns 99% of the Common Stock;

      WHEREAS, GJC owns 1% of the Common Stock;

      WHEREAS, 50 South Tenth Street is offering 700 shares of preferred stock,
$0.01 par value per share (the "Preferred Stock") to accredited investors
pursuant to that certain Confidential Memorandum dated October 1, 2006;

      WHEREAS, FSP is authorized to purchase up to 315 shares of the Preferred
Stock;

      WHEREAS, the Charter requires the affirmative vote or the written consent
of the holders of more than 50% of the then outstanding shares of the Preferred
Stock to merge or consolidate 50 South Tenth Street into or with any other
corporation or other entity or to sell all or substantially all of the assets of
50 South Tenth Street ("Merger Vote"); and

      WHEREAS, 50 South Tenth Street, FSP and GJC wish to provide for the voting
by FSP and GJC, as applicable, of the Common Stock and the Preferred Stock.

      NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties hereto agree as
follows:

      1. Common Stock. FSP and GJC agree that, in connection with any Merger
Vote, FSP and GJC shall vote the Common Stock held by them in the same manner
that a majority of the holders of shares of the Preferred Stock other than FSP
or its affiliates vote such shares in favor of or opposed to such Merger Vote.
For purposes of determining how FSP and GJC shall vote the Common Stock,
abstentions and non-votes by holders of Preferred Stock other than FSP shall not
be considered.

      2. Preferred Stock. FSP agrees that, in connection with any matter
presented for a vote by the holders of the Preferred Stock, including without
limitation any matter to be approved by written consent pursuant to Section 228
of the Delaware General Corporation Law, FSP shall vote the shares of Preferred
Stock held by it, if any, in a manner that approximates as closely as possible
the votes cast in favor of and opposed to such matter by the holders of the
Preferred Stock other than FSP and its affiliates. For purposes of determining
how FSP shall vote its shares of Preferred Stock, if any, abstentions and
non-votes by stockholders other than FSP shall not be considered.


<PAGE>

      3. FSP and GJC agree that they shall take all actions and execute all
documents reasonably requested by 50 South Tenth Street to effect the provisions
of this Agreement, including without limitation the execution and delivery of an
irrevocable proxy naming such persons designated by 50 South Tenth Street as
proxies.

      4. 50 South Tenth Street shall notify FSP and GJC as promptly as
practicable of the percentage of shares of Preferred Stock held by stockholders
other than FSP cast in favor and in opposition to any matter. 50 South Tenth
Street shall as promptly as practicable direct FSP and GJC as to how they are
required to vote in connection with any matter in accordance with the provisions
set forth above.

      5. This Agreement shall terminate upon the earlier of the following to
occur: (i) the written consent of 50 South Tenth Street, FSP and GJC or (ii) the
sale of all or substantially all of the capital stock, assets or business of 50
South Tenth Street, by merger, consolidation, sale of assets or otherwise. Upon
such termination, all rights and obligations to the parties hereto shall
terminate.

      6. All notices, requests or other communications hereunder shall be in
writing and shall be delivered (i) in person, (ii) by Federal Express or other
nationally recognized overnight carrier service which issues confirmation of
delivery or (iii) by confirmed facsimile transmission, to 50 South Tenth Street
at its principal office at 401 Edgewater Place, Suite 200, Wakefield,
Massachusetts 01880 and to FSP at its principal office at 401 Edgewater Place,
Suite 200, Wakefield, Massachusetts 01880, or to such other addresses as either
party hereto may designate to the other in writing. Any such notice shall be
deemed to be given (i) when delivered, if delivered personally or by Federal
Express or other nationally recognized overnight carrier service or (ii) upon
confirmation of receipt, if delivered by facsimile transmission.

      7. This Agreement shall be governed by and construed in accordance with
the internal substantive laws of the State of Delaware, without giving effect to
conflicts of laws principles.

      8. If any provision of this Agreement is invalid or unenforceable, such
invalidity shall not invalidate or render unenforceable any other part of this
Agreement but the Agreement shall be construed as not containing the particular
provision or provisions held to be invalid or unenforceable, and the rights and
obligations of the parties hereto shall be construed and enforced accordingly.

      9. This Agreement may be executed in counterparts, each of which shall be
deemed an original and all of which taken together shall constitute one and the
same instrument.

      10. This Agreement and any of the terms hereof may be amended, changed,
waived or discharged only by an instrument in writing signed by 50 South Tenth
Street, FSP and GJC.


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<PAGE>

      11. This Agreement is intended by the parties as a final expression of
their agreement and intended to be the complete and exclusive statement of the
agreement and understanding of the parties hereto in respect of the subject
matter contained herein. This Agreement supersedes all prior agreements and
understandings between the parties with respect to the subject matter.

      12. This Agreement shall inure to the benefit of and be binding upon the
parties hereto and their successors and permitted assigns. The obligations of
FSP and GJC hereunder shall be binding on any transferee of the Common Stock
and/or the Preferred Stock, if any, that is an affiliate of FSP. Subject to the
agreement of such affiliate to be bound hereby, FSP shall have the right to
transfer some or all of its Common Stock and/or Preferred Stock, if any, to any
of its affiliates. Except as set forth above, no party may transfer its rights
and obligations hereunder without the consent of the other parties.


                   [Signatures appear on the following page.]


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<PAGE>

      IN WITNESS WHEREOF, the parties have executed this Agreement as of the
date first written above.


50 SOUTH TENTH STREET:            FSP 50 SOUTH TENTH STREET CORP.
----------------------


                                  By: /s/ George J. Carter
                                      ---------------------
                                      George J. Carter
                                      President and Chief Executive Officer

FSP:                              FRANKLIN STREET PROPERTIES CORP.
----


                                  By: /s/ George J. Carter
                                      --------------------
                                      George J. Carter
                                      President and Chief Executive Officer


GJC:                              /s/ George J. Carter
----                              --------------------
                                  George J. Carter


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