Would someone be able to direct me to the definition of "affiliate" that the CFPB used in its guidance for the Small Creditor exemption?

There's no definition of "affiliate" given within the amendments setting up the HPML escrow requirements or within the Federal Register document in which the requirement was published.

Update: The definition is given below by Randy Carey. It wasn't in the amendments because it was already in the regulation.

From the CFPB "Ability-to-Repay and Qualified Mortgage Rule" Small Entity Compliance Guide (August 14, 2013):

Page 33 and 34

VI. What types of QM's can small creditors originate?

You can make these types of QM's only if you meet both of the following requirements:

You had assets below $2 billion (to be adjusted annually for inflation by the Bureau) at the end of the last calendar year.

You and your affiliates together originated no more than 500 first-lien, closed-end residential mortgages that are subject to the ATR requirements in the preceding calendar year.

An affiliate is any company that controls, is controlled by, or is under common control with, your company. This generally means that your affiliates are your parent company, your subsidiaries, and your sister companies. For example, if your organization is a bank owned by a bank holding company that also owns another bank, both the bank holding company and the other bank are your bank’s affiliates.

Hope this helps.

Is common ownership any amount of ownership or is there a minimum percentage of ownership or controlling interest?

In the absence of any definition in the regulation itself, I would look to Reg W, which governs transactions with affiliates. Affiliates and control are defined there.

http://www.bankersonline.com/regs/223/223-3.html

Thank you.

Affiliate is defined at 1026.32(b)(5):

(5) Affiliate means any company that controls, is controlled by, or is under common control with another company, as set forth in the Bank Holding Company Act of 1956 (12 U.S.C. 1841 et seq.).