If an undeveloped, pre-existing lot or parcel has an area which does not meet the minimum lot size requirements of the zone in which it is located, the lot or parcel may be occupied by a use permitted in the zone subject to all other applicable County and State development requirements. In zoning districts which permit multifamily dwellings, such multifamily structures shall be permitted only on a lot meeting the minimum standards of this title regarding minimum area required for multifamily dwellings.