California Code, Health and Safety Code - HSC § 51228

At the time a mortgage loan commitment is made to finance any rental or cooperative housing development, a written agreement between the agency and housing sponsor shall be executed, designating the number of units to be made available on a priority basis within such housing development to very low income households, to other persons and families of low or moderate income, and to other households. If the number of units occupied by very low income households in any housing development ever falls below the number agreed to by the agency and housing sponsor, then units which become available for occupancy shall, subject to available subsidies be made available on a priority basis to very low income households until the number of units so occupied equals at least the number specified in the agreement. The agency may from time to time review agreements designating the allocation of units and, subject to agreement with the housing sponsor, may increase the number of units to be made available to very low income households if consistent with maintenance of the financial integrity of the housing development and continuance of permitted earnings distributions, or may establish minimum rents or minimum incomes for occupancy of units becoming vacant and not otherwise allocated to very low income households if necessary to the financial integrity of the housing development and continuance of permitted earnings distributions.