I am currently looking for a comprehensive source for Building Shapefiles in the USA, particularly New Jersey. I have come across a few websites e.g. geofabrik (http://download.geofabrik.de/north-america/us/new-jersey.html), http://osm2shp.ru/ , NJDEP Bureau of GIS (https://njogis-newjersey.opendata.arcgis.com/datasets/f9fafdbecf664dae9cfb9239aae83ce7_6 ) but all seem to miss out chunks of neighbourhoods.
Thank you - here is the really comprehensive website https://blogs.bing.com/maps/2018-06/microsoft-releases-125-million-building-footprints-in-the-us-as-open-data/
data download available here: https://github.com/Microsoft/USBuildingFootprints