Maybe adding an elevator would add $150k in value? 

Don’t trust any automated screening without verifying the data put on the application is correct. 

Or perhaps the increase in value you expect from renovations?  

I cross check that against what my realtor and other local folks I have relationships with tell me about where the neighborhood is trending, as well as rent-o-meter and searching for high-level rental data/trends.

Proven fact backed by tons of research and data.

I would agree that general networking and education help lead you to a market,  but it gets overwhelming in where you turn to collect data from there. 

Interview the agents and get some market data to help you narrow down which market or markets make sense for you.  

They might not be able to give you all of the data right away, but should certainly explain the process, such as obtaining a new assessed value based on market price (your purchase price) upon sale of the property.

@Rebecca Ramos, mobile homes are a great investment to put on land if he/she is planning on renting them out, if they are on their land they will appreciate in value and if they are in parks they do as well and the great thing about them being in a park is they are taxed like a vehicle which means they are very low, everybody loves to say they lose value, they have increased in value in parks and on land tons lately, I for one am glad people still believe this cause much less competition in this area of investing

Realtor.com would be a good second bet since it pulls all MLS data.