Is the risk for a developer that they're paying for the engineering work for something the village/govt won't approve? 

I've had to hire Real Estate brokers and Professional Engineers (PEs) as "expert witnesses" for defending various false claims.Regarding #3, the smaller your project, the less likely you'll see high impact study costs.

You need to find architects/engineers in your market that deal with this type of project.In my mind, I would like to know what the per unit cost is of each unit.

Every jurisdiction is different, but in general it's usually a civil engineer and/or architect and/or general contractor who can give you an idea of what is feasible. 

Hi @elisha  I am a land planner working for a civil engineering firm in Alpharetta.

An additional benefit of a detailed engineering-based Cost Segregation Study is that it can increase potential insurance premium savings as well as provide support for the property tax appeals process.

They are engineering those returns by over raising equity.  

The best route is using licensed foundation companies and engineers to conduct work surveys to determine what needs to be done and then having that work done by licensed companies with warranties. 

The designation for Certified Cost Segregation professional is CCSP and comes after the engineer’s name.

Check with the building permit department about exact submission requirements and what work requires licensed designers and engineers.