Exhibit 10.6

FOURTH AMENDMENT TO

AGREEMENT FOR SALE AND PURCHASE OF PROPERTY

This Fourth Amendment to Agreement for Sale and Purchase of Property (the
“Amendment”) is made and entered into effective as of the 12th day of July,
2010, by and between DAKOTA HILL PROPERTIES, A TEXAS LIMITED PARTNERSHIP
(“Seller”), and KBS REALTY ADVISORS, LLC, a Delaware limited liability company
(“Buyer”).

A.        Buyer and Seller entered into that certain Agreement for Sale and
Purchase of Property dated as of the 31st day of March, 2010, that certain First
Amendment to Agreement for Sale and Purchase of Property dated as of May 25,
2010, that certain Second Amendment to Agreement for Sale and Purchase of
Property dated as of June 10, 2010 and that certain Third Amendment to Agreement
for Sale and Purchase of Property dated as of July 2, 2010 (collectively, the
“Agreement”). Capitalized terms used but not defined in this Amendment shall
have the meanings assigned to such terms in the Agreement. Subject to the terms
set forth in the Agreement, Buyer has agreed to purchase the Property from
Seller.

B.        Buyer and Seller desire to and hereby amend the Agreement on all of
the terms, provisions and conditions contained herein.

In consideration of the mutual covenants and agreements contained herein and
other good and valuable consideration, the receipt and sufficiency of which are
hereby acknowledged, the parties, intending to be legally bound, agree as
follows:

1.        Section 6.3 of the Agreement shall be amended to provide that the
Inspection Date shall be the 16th day of July, 2010.

2.        This Amendment is integrated into and made a part of the Agreement.
Except as specifically otherwise specifically provided herein, all other terms
and conditions of the Agreement, as hereby amended, are ratified and confirmed
and shall remain unchanged and in full force and effect. In the event of any
conflict between this Amendment and the Agreement, the terms and conditions of
this Amendment shall govern and control. Seller and Buyer have obtained any and
all necessary consents and/or approvals prior to executing this Amendment. This
Amendment may be executed in multiple counterparts, which when taken together
shall constitute one and the same instrument. Executed counterparts of this
Amendment transmitted by facsimile or email shall bind the party so signing with
the same effect as though the signature were an original signature.

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

 

Seller: DAKOTA HILL PROPERTIES, A TEXAS LIMITED PARTNERSHIP
By:   DAKOTA IRET, Inc., a Texas corporation, its general partner   By:   /s/
Thomas A. Wentz, Jr.     Print Name: Thomas A. Wentz, Jr.     Print Title: Vice
President   By:   /s/ Michael A. Bosch     Print Name: Michael A. Bosch    
Print Title: Secretary Buyer:
KBS REALTY ADVISORS, LLC, a Delaware limited liability company By: /s/ Charles
J. Schreiber, Jr. Print Name: Charles J. Schreiber, Jr. Print Title: Chief
Executive Officer