(d) The state, acting by and through the Commissioner of Housing, may enter into a contract with a mutual housing association to provide financial assistance for the development of housing for low and moderate income families. State financial assistance provided under this subsection may be in the form of grants, loans, deferred loans or any combination thereof and may be used for the acquisition or development of housing sites and for the costs incurred in the development of such housing. Contracts for state financial assistance provided under this subsection shall provide that the mutual housing association: (1) Require resident members to pay a membership fee as a condition of eligibility for occupancy of a dwelling unit, provided such membership fee shall be refundable to the resident member, with nominal interest, when the resident member vacates such unit; (2) may allow, in fixing the rentals for dwelling units, for a reasonable return on equity capital contributed to the development of such housing through mutual housing association membership fees or grants obtained from sources other than the state, provided such return on equity capital shall be utilized by the association to develop additional dwelling units; and (3) shall permit continued occupancy by resident members whose incomes rise above low and moderate income limits, provided the rent to be paid for such continued occupancy shall be fixed at a level not less than twenty-five per cent of the resident members' adjusted household income, and provided any increased rent collected for continued occupancy shall be used by the association to develop additional dwelling units for low and moderate income families or shall be credited against the rent owed by another low or moderate income resident member of