From the forum over at Brownstoner:
How many can live in 1 family house?
One of the commenters dug this up:
"NYC Housing Guidelines: Sec. 27-2075 Maximum permitted occupancy
No dwelling unit shall be occupied by a greater number of persons than is permitted by this section.
Every person occupying an apartment in a class A or class B multiple dwelling or in a tenant-occupied apartment in a one- or two-family dwelling shall have a livable area of not less than eighty square feet. The maximum number of persons who may occupy any such apartment shall be determined by dividing the total livable floor area of the apartment by eighty square feet. For every two persons who may lawfully occupy an apartment, one child under four may also reside therein, except that a child under four is permitted in an apartment lawfully occupied by one person. No residual floor area of less than eighty square feet shall be counted in determining the maximum permitted occupancy for such apartment.
The floor area of a kitchen or kitchenette shall be included in measuring the total liveable floor area of an apartment but the floor area for private halls, foyers, bathrooms or water closets shall be excluded.
A living room in a rooming unit may be occupied by not more than two persons if it has a minimum floor area not less than one hundred ten square feet in a rooming house, or one hundred thirty square feet in a single room occupancy."
Now good luck getting this enforced.