Prior to the issuance of a building permit for the construction of any dwelling unit within an affordable housing development, the owner shall execute and record in the Cumberland County Registry of Deeds a declaration of covenants encumbering the entire affordable housing development, in a form that has been reviewed and approved by the Town Attorney. This declaration of covenants must provide that for a period of at least 30 years after completion of construction of an affordable housing development, the occupancy of at least 51% of the dwelling units therein shall remain limited to households whose taxable income is at or below 80% of local area median income for rental housing (or 120% of local area median income for owned housing), at the time of initial occupancy. Such restrictive covenants shall be enforceable by the Town of Gorham or its designee.