(b) If two or more principal residential structures or dwelling units are located on the same lot, where the lot was created before the effective date of this chapter, the minimum lot area per dwelling unit requirement and all other requirements of this chapter and other applicable laws, rules, and regulations must be strictly met. Further, a residential lot of required or greater than required area, as set forth in this chapter, shall not be reduced in area by transfer of ownership if such lot so divided will form two or more lots, any of which shall be less than the minimum lot area required for the zoning district in which the lot or lots are situated.