NY research options:

New York Public Library-
Museum of the City of New York-
American Memory from the Library of Congress (great searchable database of historic images in the public domain)-
The Building Permits Database, 1900-1986

Selling NY rare books and prints- I can't help here. Contact NY print and art dealers directly.

Useful NYC Books:

"AIA Guide to New York City". ISBN 0812931076.
"New York 1880: Architecture and Urbanism in the Gilded Age."
Robert A.M. Stern, Thomas Mellins, and David Fishman
New York: The Monacelli Press, 1999
"New York 1900: Metropolitan Architecture and Urbanism 1890-1915."
Robert A.M. Stern, John M. Massengale, and Gregory Gilmartin
New York: Rizzoli International Publications, Inc., 1983
"New York 1930: Architecture and Urbanism between the Two World Wars."
Robert A.M. Stern, Gregory Gilmartin, and Thomas Mellins
New York: Rizzoli International Publications, Inc., 1987

Urban Centre Bookstore-