Adequate off-street parking facilities shall be provided to accommodate all motor vehicles of residents or employees, visitors, and customers, and the vehicles used in the conduct of any business enterprise, and no such required off-street parking shall be leased, rented, or otherwise made available on an optional basis so as to allow the tenant of a use to elect not to pay the extra fee which could result in the parking not being available for the use to which it is accessory. Notwithstanding the above provision, in no case shall the number of off-street parking spaces provided be less than the minimum prescribed in this Zoning Code.