No mortgage shall be insured under this section unless (1) the housing which is covered by the insured mortgage is necessary in the interest of national security in order to provide adequate housing for (A) military personnel and essential civilian personnel serving or employed in connection with any installation of one of the armed services of the United States, or (B) essential personnel employed or assigned to duty at or in connection with any research or development installation of the National Aeronautics and Space Administration or of the Atomic Energy Commission, (2) there is no present intention to curtail substantially the number of such personnel assigned or to be assigned to the installation, (3) adequate housing is not available for such personnel at reasonable rentals within reasonable commuting distances of such installation, and (4) the mortgaged property will not so far as can be reasonably foreseen substantially curtail occupancy in any existing housing in the vicinity of the installation which is covered by mortgages insured under this chapter.
The Secretary shall require each project covered by a mortgage insured under this section to be held for rental for a period of not less than five years after the project or dwelling is made available for initial occupancy or until he finds that the housing may be released from such rental condition. The Secretary shall prescribe such procedures as in his judgment are necessary to secure reasonable preference or priority in the sale or rental of dwellings covered by a mortgage insured under this section for military personnel and essential civilian employees of the armed services, employees of contractors for the armed services, and persons described in clause (1)(B) of subsection (b) of this section.
For the purpose of providing multifamily rental housing projects or housing projects consisting of individual single-family dwellings for sale, the Secretary is authorized to insure mortgages (including advances on such mortgages during construction) which cover property held by a mortgagor approved by the Secretary. Any such mortgagor shall possess powers necessary therefor and incidental thereto and shall until the termination of all obligations of the Secretary under such insurance be regulated or restricted as to rents or sales, charges, capital structure, rate of return, and methods of operation to such extent and in such manner as to provide reasonable rentals to tenants and a reasonable return on the investment. The Secretary may make such contracts with, and acquire for not to exceed $100 such stock or interest in, any such mortgagor as he may deem necessary to render effective such restriction or regulation. Such stock or interest shall be paid for out of the General Insurance Fund, and shall be redeemed by the mortgagor at par upon the termination of all obligations of the Secretary under the insurance.
To be eligible for insurance under this section, a mortgage on any multifamily rental property or project shall involve a principal obligation in an amount not to exceed, for such part of such property or project as may be attributable to dwelling use, $9,000 per family unit without a bedroom, $12,500 per family unit with one bedroom, $15,000 per family unit with two bedrooms, and $18,500 per family unit with three or more bedrooms, and not to exceed 90 per centum of the estimated value of the property or project when the proposed physical improvements are completed. The Secretary may, by regulation, increase any of the foregoing dollar amount limitations contained in this paragraph by not to exceed 45 per centum in any geographical area where he finds that cost levels so require.
To be eligible for insurance under this section a mortgage on any property or project constructed for eventual sale of single-family dwellings shall involve a principal obligation in an amount not to exceed a sum computed on the basis of a separate mortgage for each single-family dwelling (irrespective of whether such dwelling has a party wall or is otherwise physically connected with another dwelling or dwellings) comprising the property or project equal to the total of each of the maximum principal obligations of such mortgages which would meet the requirements of section 1709(b)(2) of this title if the mortgagor were the owner and occupant who had made the required payment on account of the property prescribed in such paragraph.
Any mortgage insured under this section shall provide for complete amortization by periodic payments within such terms as the Secretary may prescribe but not to exceed the maximum term applicable to mortgages under section 1713 of this title and shall bear interest at such rate as may be agreed upon by the mortgagor and the mortgagee, except that individual mortgages of the character described in subsection (g) covering the individual dwellings in the project may have a term not in excess of the maximum term applicable to mortgages insured under section 1709 of this title or the unexpired term of the project mortgage at the time of the release of the mortgaged property from such project mortgage, whichever is the greater, and shall bear interest at such rate as may be agreed upon by the mortgagor and the mortgagee. The Secretary may consent to the release of a part or parts of the mortgaged property from the lien of the mortgage upon such terms and conditions as he may prescribe and the mortgage may provide for such release, and a mortgage of the character described in subsection (g) of this section may provide that, at any time after the release of the project from the rental period prescribed by subsection (d), such mortgage may be replaced, in whole or in part, by individual mortgages covering each individual dwelling in the project in amounts not to exceed the unpaid balance of the blanket mortgage allocable to the individual property. Each such individual mortgage may be insured under this section. Property covered by a mortgage insured under this section may include eight or more family units and may include such commercial and community facilities as the Secretary deems adequate to serve the occupants.
The aggregate number of dwelling units (including all units in multifamily projects or individual dwellings) covered by outstanding commitments to insure and mortgages insured under this section shall at no time exceed five thousand dwelling units.
The provisions of subsections (d), (e), (g), (h), (i), (j), (k), (l), and (n) of section 1713 of this title shall be applicable to mortgages insured under this section except individual mortgages of the character described in subsection (g) of this section covering the individual dwellings in the project, and as to such individual mortgages the provisions of subsections (a), (c), (d), (e), (f), (g), (h), (j), and (k)  of section 1710 of this title shall be applicable: Provided, That wherever the words “Fund” or “Mutual Mortgage Insurance Fund” appear in section 1710 of this title, such reference shall refer to the General Insurance Fund with respect to mortgages insured under this section.
The provisions of sections 1748, 1748a,1 1748b(c), 1748b(i), 1748b(j), 1748c(a), 1748c(b),1 and 1748f of this title and the provisions of section 1748b(a) of this title relating to the aggregate amount of all mortgages insured under this subchapter shall be applicable to mortgages insured under this section.