With the growing popularity of services like AirBnB, a light has been shed on New York's illegal hotels.
These are apartment units, which are intended to be occupied by long term tenants, being rented out by the owner or a “tenant” who has rented a block of apartments, for transient use. This is illegal. Unlike AirBnB, which is a temporary measure tenants can offer when they leave their apartment vacant for a temporary period of time, illegal hotel rooms are permanent.
It's easy to see why people are drawn to this practice. Hotels are required to have a proper certificate of occupancy, the use must comply with zoning requirements, and the building requires added safety features that an apartment does not (For example, fire safety features and accommodations for the handicapped). Offering an apartment for rent provides easy income with low overhead start up costs.
It is also easy to see why this is illegal. Apartment buildings are not designed for the denser occupancy of hotels. A constant flow of transient tenants can cause excessive noise, and disrupt neighbors who live in the building legally. Longterm tenants may also be concerned about their safety, with the high traffic of strangers through their building. Illegal hoteliers sometimes use key card systems instead of keys, which proper tenants may find problematic for a number of reasons.
Finally, these "hotels" are breeding grounds for bed bugs, which are primarily spread by transient tenants in New York.