In my experience, this data has been at no cost. Most property appraiser sites offer sales data as an excel file for download. Each property can be looked at with exterior photos, or base floor plans. It would take quite alot of dara entry to input into a program, the issue would be the accur...
Separate, but related note: "NYC Open Data" is growing every day & provides free data https://opendata.cityofnewyork.us/ For national data check out the parent organization Socrata.com. Great resources for public data records, which are 100% free, contains everything from real estate transaction...