In the C-1, C-2, I-1, I-2, M and APZ-I or II zones, lawfully existing and established residential uses as of January 1, 1970, shall be considered conforming and allowed to continue until abandoned. Maintenance, repair, and replacement of existing structures, improvements and buildings shall be allowed. Expansion and replacement of existing residential structures shall be permitted as long as no additional dwelling units are created. Expansion and replacement of existing residential uses shall adhere to the setbacks, building coverage and height, minimum lot area and frontage requirements. Expansion and replacement of residential structures not in a residential zone shall conform to the specifications set forth in the residential zone in which the use most closely resembles; except, replacement that does not exceed the prior footprint shall be permitted subject to the setback regulations at the time the structure was established and placed in use. Previously permitted residential uses that do not currently exist, where the use of the property has not changed, can be reestablished if the property owner can demonstrate the previous use. Adding structures to the nonconforming use is permitted and will follow the regulations of the closest zoning.