Exhibit 10.1

SECOND AMENDMENT TO OTHER INTEREST AGREEMENT

This Second Amendment (this “Amendment”) to the Other Interest Agreement, dated as of December 2, 2011 (as amended on February 17, 2012, the “Agreement”), by and among ERP Operating Limited Partnership, an Illinois limited partnership (“Equity”), and each of BIH ASN LLC (“BIH”), Archstone Equity Holdings Inc. (“AEH” and, collectively with BIH, “Barclays”), Bank of America, N.A. (“BANA”) and Banc of America Strategic Ventures, Inc. (“BofA Strategic”, and, collectively with BANA, “Bank of America”), is made effective as of April 18, 2012, by and among Equity, Barclays and Bank of America. Barclays and Bank of America are sometimes referred to herein as “Owners” and, each, an “Owner.” Equity and Owners are sometimes referred to herein as the “Parties” and each, a “Party.”

RECITALS:

WHEREAS, the Parties entered into the original Agreement on December 2, 2011 and entered into the First Amendment to the Agreement on February 17, 2012;

WHEREAS, the Parties desire to amend the Agreement as set forth in this Amendment; and

WHEREAS, capitalized terms used in this Amendment and not defined herein shall have the meanings ascribed to such terms in the Agreement, or, if not defined in the Agreement, in the Interest Purchase Agreement, as if the Interest Purchase Agreement remained in full force and effect.

NOW, THEREFORE, in consideration of the foregoing and other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the Parties, intending to be legally bound hereby, agree as follows:

“Subject to the preceding sentence, Equity shall have the right to exercise the Option by providing written notice to Owners (the “Exercise Notice”) at any time during the period commencing on the ROFO Acquisition Date and ending at 5:00 p.m. Eastern time on May 21, 2012 for a purchase price, payable in cash, in an amount set forth in the Exercise Notice that is greater than or equal to $1,500,000,000.”

“9. Termination. This Agreement shall terminate automatically and simultaneously on the earlier to occur of (i) 5:00 p.m. Eastern time on May 21, 2012, if the Option has not been exercised, and (ii) the termination of the Other Interest Purchase Agreement; provided, however, that Section 12 hereof shall survive any such termination in accordance with its terms.”

[Signature Page Follows]

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IN WITNESS WHEREOF, the Parties have executed and delivered this Amendment as of the date set forth above.

Signature Page to Second Amendment to Other Interest Agreement