I'm looking to combine geographic data to determine the best zones to look into investing.

How do you find the data for sold units in the area for the past 3 years?

I do web research, data entry, and other stuff.

I know there is a Denver based company called AirDNA that researches data in Airbnb markets all over the world but I have heard from people using Airbnb to rent out their properties that some of their data is very far off.

Stable, well-protected midwest cities like Pittsburgh are going to rise in value as places to do business as things get worse elsewhere.

Even an economic recession at the macro level may only lead to a slow down/plateau in this market, vs. a dip in values/rents.

What I am really after are the look alike audiences and putting the Facebook data engine to work for me. 

The City of Austin has entered into a pilot contract with Seattle-based company, Host Compliance, to provide data on short-term rentals in the city.

Some subdivisions, as well as rental rates, will increase in value with the addition of a bedroom.

@Max Pallatt, the data backs up your notion.