(a) "Dwelling" means any building or portion thereof which is designated for or used for residential purposes.
(b) "Single-family dwelling" means a building designed for or occupied exclusively by one family.
(c) "Two-family dwelling" means a building designed for or occupied exclusively by two families.
(d) "Multiple dwelling" means a building used or designed as a residence for there or more families living independently of each other and doing their own cooking therein, including apartment houses, garden apartments and row houses.