One of the most comprehensive collections for New York City architectural drawings is the Manhattan Building Plan Collection at the Municipal Archives. The plans typically include drawings for buildings built between 1866-1970s, that were still standing from 1971 on. This collection is still being processed, but some digitized plans are available online. Contact the Municipal Archives for further advice.
Above top, Plan for the 1st floor of 385 Avenue of the Americas, from 1948: as a liquor store, and as a projected diner (below), the Waverly Diner. (Manhattan Building Plan Collection, Courtesy the Municipal Archives).
Though NYPL does not have extensive collections of architectural drawings, it is possible that collections might include drawings and floor plans for a building.
Try using keyword terms to find useful subject terms in NYPL Research Catalog to locate published materials that may include architectural drawings, blueprints, or floor plans. For instance
Search in NYPL Archives using the name or address of a building, the architect, builder, or owner, for instance.
NYPL Digital Collections includes
Some I-Cards include rough drawings of a residential building's floor plan.
Sanborn Fire Insurance maps sometimes give clues to a building's layout, but seldom for residential buildings.
Again, librarians in the NYPL Art and Architecture Collection can advise you on researching architects. Some useful resources include:
Left, Obituary for architect David Jardine, who's firm D. & J. Jardine designed the building that became the Waverly Diner. New York Tribune, June 2, 1892, p.5 (ProQuest Historical Newspapers)