; and (bb) in the case of a 2-, 3-, or 4-family residence, the percentage of such median price that bears the same ratio to such median price as the dollar amount limitation determined under the sixth sentence of section 305(a)(2) of the Federal Home Loan Mortgage Corporation Act ( 12 U.S.C. 1454(a)(2) ) for a 2-, 3-, or 4-family residence, respectively, bears to the dollar amount limitation determined under such section for a 1-family residence; or (II) 150 percent of the dollar amount limitation determined under the sixth sentence of such section 305(a)(2) for a residence of the applicable size. For purposes of the preceding sentence, the term area means, for any property located within a metropolitan statistical area as established by the Office of Management and Budget, the zip code within which the property is located, and for any property not located within a metropolitan statistical area, the county within which the property is located. The dollar amount limitations referred to in this clause shall remain in effect for purposes of this clause notwithstanding the receivership or dissolution of the Federal Home Loan Mortgage Corporation. (ii) Minimum limit Notwithstanding clause (i), the principal obligation limitation in effect for any area under this subparagraph may not be less than $200,000. (2) Downpayment The mortgage shall be executed by a mortgagor who shall have paid on account of the property subject to the mortgage an amount, in cash or its equivalent, equal to or exceeding 3.5 percent of the appraised value of the property, as determined by the FHA. (3) Prohibited mortgages The mortgage is not— (A) a mortgage the proceeds of which are used to prepay or pay off an existing loan that is not— (i) a loan insured under the National Housing Act or under this title; or (ii) a loan insured, made, or guaranteed under title V of the Housing Act of 1949