City Data seems to work pretty well for me.

If I run on current data, I come up with one offer, and different scenarios yield different offers.

Indoor RV and boat storage - easy conversion and your location on the way to Canyon Lake would be ideal.Talk to all the data storage companies in Austin and San Antonio about space for server farms.

Lazy data entry. 

You can do this on redfin, zillow or just have your realtor pull comps from MLS data.

The tower companies decide all on their own based on all kinds of data and metrics they determine. 

@Ryan Dossey do you find Skip Genie to provide accurate data?

It is amazing how many people use initial cash flow as though it is the only item that dictates total return.I am not an expert on San Antonio, but if it were my property I would look at indicators like population growth, vacancy rates, quality of jobs and schools, wage increases, historical appreciation data, etc. and use that data to determine the likelihood of market and rent appreciation. 

From what I see on the city tax assessors website there has been an average 2.8%/year appreciation for the last 16 years (all the data I have on the website).

*Section twenty-six prohibits the Office of Court Administration fromselling housing court data to third parties.