Each year, the Rent Guidelines Board (RGB) establishes the lease guidelines for rent stabilized apartments. Apartments in buildings rehabilitated or newly constructed after January 1, 1974 are not rent regulated unless the owner has taken advantage of special tax abatement programs known as the J-51 and 421-a programs. There are a number of exceptions to these generalizations. Market-Rate Housing includes apartments which have never been regulated and apartments which have undergone deregulation. Vacant apartments in buildings with one to five units are generally not rent regulated.