Here is a link to Columbia University's Digital Archive collection of Vintage Real Estate Brochures.
The collection consists of over 9,200 advertising brochures, floor plans, price lists, and related materials that document residential and commercial real estate development in the five boroughs of New York and outlying vicinities from the 1920s to the 1970s.
Here you will find plans and renderings of many pre-war apartment buildings. Great for base-plans if you are renovating a NYC apartment or just general interest in how these buildings are laid out. Enjoy!
https://dlc.library.columbia.edu/nyre/