any other mortgagor approved by the Secretary. The Secretary may, in the Secretary’s discretion, require any such mortgagor to be regulated or restricted as to rents or sales, charges, capital structure, rate of return, and methods of operation so as to provide reasonable rentals to tenants and a reasonable return on the investment. Any such regulations or restrictions shall continue for such period or periods as the Secretary, in the Secretary’s discretion, may require, including until the termination of all obligations of the Secretary under the insurance and during such further period of time as the Secretary shall be the owner, holder, or reinsurer of the mortgage. The Secretary may make such contracts with and acquire, for not to exceed $100, such stock or interest in the mortgagor as he may deem necessary to render effective any such regulations or restrictions. The stock or interest acquired by the Secretary 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.