Reflecting upon historical and recent events, I can't help but appreciate our note investing niche.

Chicago also has an old historic set of watermark drawings that you can sometimes request, but I am still not sure of that process. 

I believe AirDNA is a great source too and of course just seeing what comps are currently renting for and historically depending on the seasons

Contact the utility provider and get an historical average based on the last year of use.

I've seen beach homes, historic homes, and everyday homes.

With rates still at historic lows, we have had a number of investors who took out HELOCs recently to invest in our recent syndication deals. 

Also, for most large commercial properties a bank will want a new LLC created to ensure there are no historical liabilities.

Are you in a historic district?  

Im looking to view historical price trends in America for each state, as far back as possible.

A 3.125% interest rate is still very historically low, and you can definitely find a property that brings you a much better coc return than that annually and you also benefit from the other advantages of owning real estate.