this is fairly common practice in low income areas Ideally you’d never do this but in some rough neighborhoods where everyone is on assistance it sure can help

Outside of this, it may help to start with a few basic online sources (rentometer.com, CraigsList, etc) to give you a jumping off point and some rough market insight.  

What are some best practices?

@John Thedford and everyone: (Disclosure- I am not licensed to practice law in Florida, or anywhere else!)

Property listed online (Trulia, Zillow, etc..) and is well below market value and appears to be depressed. ~ I'm thinking this is a shortsale2.

@Eric Veronicayeah the per unit min was surprising to me as well, mentioned nothing in the online application...The subject property is 4 units, future properties would be 2-4 (that 1-4 was a typo)

I found the property online and it's been listed for over 90 days. 

Your contractor should have at least communicated this with you when before incurring the cost of the extra material, best practices is to provide you with a change order as an amendment to the contract.

I look online at the BAH that a SSgt earns. 

I got his number from a inspection report that was filed online and is public record.