The agency may establish a tenant-based or project-based rental housing assistance program for persons of low income or for persons with a mental illness or families that include an adult family member with a mental illness. Rental assistance may be in the form of direct rental subsidies for housing for persons or families with incomes, at the time of initial occupancy, of up to 50 percent of the area median income as determined by the United States Department of Housing and Urban Development, adjusted for families of five or more. Housing for the mentally ill must be operated in coordination with social service providers who provide services requested by tenants. Direct rental subsidies must be administered by the agency for the benefit of eligible tenants. Financial assistance provided under this section must be in the form of vendor payments whenever possible.