This part implements section 9(f) of the United States Housing Act of 1937 (1937 Act), (42 U.S.C. 1437g). Section 9(f) establishes an Operating Fund for the purposes of making assistance available to public housing agencies (PHAs) for the operation and management of public housing. In the case of unsubsidized housing, the total expenses of operating rental housing should be covered by the operating income, which primarily consists of rental income and, to some degree, investment and non-rental income. In the case of public housing, the Operating Fund provides operating subsidy to assist PHAs to serve low, very low, and extremely low-income families. This part describes the policies and procedures for Operating Fund formula calculations and management under the Operating Fund Program.