(FORTUNE Magazine) – Call him the Medici of middle-income housing. Samuel LeFrak, 71, New York City's billionaire landlord, wants the world to know that underneath his brick-and-mortar exterior lies the soul of an artist. LeFrak collects art almost as avidly as he collects rents. Recently he bought from an Italian family a portrait of Paul Gauguin that he believes was painted by Vincent van Gogh. Art experts in Paris are examining the work, and if it is authentic, it would be a remarkable discovery -- the equivalent, say, of finding a $400-per- month apartment in Manhattan. Meanwhile LeFrak is giving art historians a peek at the rest of his collection by publishing a book filled with reproductions of his favorites. The book's frontispiece is a portrait of LeFrak and his wife, Ethel, done in 1982 by the late Andy Warhol. Back when Warhol was just a struggling artist, LeFrak offered him $500 to decorate the bathroom and kitchen of a model apartment in Lefrak City, a sprawling residential complex in Queens. Warhol covered the walls and cabinets with colorful ducks and teakettles. Then Warhol went on to fame via Campbell Soup cans, and the apartment was repainted. No one knows which of the 5,000 apartments in Lefrak City is the one Warhol decorated. Says LeFrak: ''Warhol's work is hiding underneath the paint in someone's apartment.''