It's a fairly unregulated space (charging grandma $750 to puts around for 3 hours, after moving the old box from the horizontal sensor, which was the only problem with the garage door to begin with), so some combination of carefully reading reviews (you have to actually read them to make sure it's not 200 fake reviews), and maybe not giving them the full contract all at once, is in order. 

I bet we would have made around $100k as a wholesale.

The reality is the opposite - if it's not in writing then the PMC doesn't have to provide the service or can charge extra for it!

Moving forward scaling with hard money loans may be the best bet and would avoid the headaches of living in a construction project. 

Patio door prices can depend on the Model of Patio door you are looking for, for a standard 60x80 in white it will cost $1900.00 colors can be added, and for a patio door 72x80 the cost will be $2100.00 Outswing for a 60x80 will cost $2600.00 installed, and for an outswing 72x80 it will cost $2700.00 installed outswing with Grills for a 60x80 costs $1860.00, and an outswing 72x80 will cost $2300.00 installed.You also add blinds to all sliding and outswing patio doors for an additional charge.

What is he charging for the materials?

Most of these brokerages charge minimum fees to keep your license active while still maintaining your license.

Also make sure to build on a property located in a desirable location with larger pop density and if holding for rentals, charge median rent for that market as lenders want to see a bigger pool of buyers/renters available to occupy/sell. 

You bet.

Note: Florida charges a hefty tax on rentals under 6 months.