There is hereby established in the District of Columbia and there is authorized, and accounted for in the General Fund as a separate revenue source allocable to provide financial assistance to low and moderate income persons, and District of Columbia Government employees participating in the District of Columbia Employer-Assisted Housing Program, and families seeking to purchase homes in the District of Columbia, for the purposes of enabling them to purchase decent, safe, and sanitary homes in the District of Columbia. Any unexpended balance at the end of the year shall be reserved as a restricted fund balance and used to provide authorization to expend for subsequent years subject to the direction of the Mayor.