Local building code by me says we can have up to two layers of shingles and still be ok though.

flat or shingles?

Majority of roofers we contacted work with shingles only or will only work with commercial flat roofs.  

If you're interested, you can check out my broker, Summa Real Estate Group, there are several real estate investors "hanging their shingle" with us and the principle is an investor as well.BTW, I passed my state and federal exams the first time through. :-)

Needs new roof, shingles, trim, deck and chimney.- Purchase price $310K.  

We would bid a job, but there was a clause that replacing bad sheeting (plywood under shingles) was billed separately per square foot for materials and by the hour for labor.

Prices are about 185 per square for architectural shingles installed.

Or, can you simply hang your shingle with a broker and work as much, or as little, as you'd like?

It is just a block construction shingle roof building.

A few years ago I got tired of paying roofing guys $150 - $300 to replace missing shingles.