I don't know if this helps or confuses the matter...
There is no federal legislation to standardize the enforcement of apartment occupancy laws. Though the Keating Memorandum of 1991 states that a policy of two people to a bedroom seemed sound to the Department of Housing and Urban Development (HUD), there is no language in the Fair Housing Act that directly addresses either the number or relationship of people legally allowed to occupy an apartment.
The article goes on to say...
While many states and municipalities have apartment occupancy laws on the books, just as many do not. The legalities in the neighboring towns may be very different and most primarily leave occupancy restrictions up to property owners and managers. Apartment A may regulate occupancy according to the guidelines set forth in Keating -- two persons per bedroom. Apartment B may modify those standards to not include small children in their occupancy count, and apartment C may adhere to the Building Officials and Code Administrators (BOCA) guidelines that state, "Every dwelling unit must contain a minimum gross floor area not less than 150 square feet for the first occupant and 100 square feet for each additional occupant. Every room occupied for sleeping purposes by one occupant shall contain at least 70 square feet of floor area, and every room occupied for sleeping purposes by more than one person shall contain at least 50 square feet of floor area for each occupant." Tenants have little recourse in apartment occupancy disputes unless they can prove that enforcement will result in discriminatory practices.
Of course, this example is for an apartment. The point is it seems as though there are no set and concrete laws or regulations.
Apartment Occupancy Laws | eHow.com