Contractors who do work in New York City and Nassau, Suffolk, Putnam, Rockland and Westchester counties must be licensed by local authorities. Several localities also have licensing requirements. Several localities also have additional licensing requirements.
Check with your local authority about licensing requirements. If you live in a jurisdiction that licenses contractors, be sure to only hire a duly licensed contractor. Hiring a licensed contractor offers many protections to the property owner, especially if you experience problems with the work.