1. Any marketplace references, such as Zillow, Redfin, and even county sales records, timely to Real Estate held and sold, will do and should be kept on file. Right now I am working on this for a place in FL and Pinellas County has a great sales database, which I used to look at Zillow listing prices for the 6 months prior to sale date.

2. I learned a new trick recently: pull the credit report of the deceased. It might reveal something you didn't know about. I like to wait over two year ends, just in case stuff shows up late in the mail, before final distribution and closing.