a. A family may rent one or more living rooms in an apartment to not more than two boarders, roomers or lodgers, if every living room in such apartment has free and unobstructed access to each required exit from such apartment as provided in paragraphs (a), (b) and (c) of subdivision four of section two hundred forty-eight or paragraph (a) of subdivision one of section fifty-three of the multiple dwelling law, and if each such boarder, roomer or lodger has access to, and the right to use, at least one water closet, bath or shower and one washbasin as may be required in or for an apartment in this code.
b. Where a tenant rents any part of an apartment in a multiple dwelling to more than two boarders, roomers or lodgers, such rental shall constitute a use of the apartment for single room occupancy and such rental in an apartment of a converted dwelling shall constitute an unlawful use as a rooming unit.
c. A family may rent one or more living rooms in a private dwelling to not more than two boarders, roomers or lodgers, except as otherwise prohibited under the zoning resolution of the city of New York.