12 USC 1715z16 - Adjustable rate single family mortgages

(a) One- to four-family dwellings; maximum term of mortgage; adjustments in effective rate of interest 
The Secretary may insure under any provision of this subchapter a mortgage involving property upon which there is located a dwelling designed principally for occupancy by one to four families, where the mortgage provides for periodic adjustments by the mortgagee in the effective rate of interest charged. Such interest rate adjustments may be accomplished through adjustments in the monthly payment amount, the outstanding principal balance, or the mortgage term, or a combination of these factors, except that in no case may any extension of a mortgage term result in a total term in excess of 40 years. Adjustments in the effective rate of interest shall correspond to a specified national interest rate index approved in regulations by the Secretary, information on which is readily accessible to mortgagors from generally available published sources. Adjustments in the effective rate of interest shall
(1)  be made on an annual basis;
(2)  be limited, with respect to any single interest rate increase, to no more than 1 percent on the outstanding loan balance; and
(3)  be limited to a maximum increase of 5 percentage points above the initial contract interest rate over the term of the mortgage.
(b) Written explanation of mortgage features 
The Secretary shall require that the mortgagee make available to the mortgagor, at the time of loan application, a written explanation of the features of an adjustable rate mortgage consistent with the disclosure requirements applicable to variable rate mortgages secured by a principal dwelling under the Truth in Lending Act [15 U.S.C. 1601 et seq.].
(c) Number of mortgages and loans 
The aggregate number of mortgages and loans insured under this section in any fiscal year may not exceed 30 percent of the aggregate number of mortgages and loans insured by the Secretary under this subchapter during the preceding fiscal year.
(d) Adjustable rate mortgage with initial fixed rate of interest 

(1) The Secretary may insure under this subsection a mortgage that meets the requirements of subsection (a) of this section, except that the effective rate of interest
(A) shall be fixed for a period of not less than the first 3 years of the mortgage term;
(B) shall be adjusted by the mortgagee initially upon the expiration of such period and annually thereafter; and
(C) in the case of the initial interest rate adjustment, is subject to the 1 percent limitation only if the interest rate remained fixed for 3 or fewer years.
(2) The disclosure required under subsection (b) of this section shall be required for a mortgage insured under this subsection.