She was also able to rent the house out for me for a flat fee to a great tenant, for more than I thought it was worth. 

I own a two flat now in my name.

The mobile home industry is vast (roughly 8% of the U.S. population lives in a mobile home) and customers range from McDonald's employees to billionaires (in the Montauk park in the Hamptons) and even movie stars (Pam Anderson, Hillary Duff, etc. in Malibu).Make sure you understand the rules from HUD on remodeling mobile homes, such as the fact that you can't enlarge windows or doors or increase the weight on the exterior walls (for example replacing paneling with drywall).

New roof, new AC, moving electric panel (fortuneatly electrical had already been updated and house had been replumbed), new flooring throughout, new kitchen, new M bathroom, updating 2nd bath.

New roof, new AC, moving electric panel (fortuneatly electrical had already been updated and house had been replumbed), new flooring throughout, new kitchen, new M bathroom, updating 2nd bath.

New roof, new AC, moving electric panel (fortunately electrical had already been updated and house had been re-plumbed), new flooring throughout, new kitchen, new M bathroom, updating 2nd bath.

Well, since you can't rip the walls to look at framing, wiring, and plumbing, look at what you can see:1) Level of trim, appliances2) Finish carpentry or gaps in joints3) The flatness of floors and squareness of rooms. 

Is there a Chicago specific directory of average costs for things, like price per sf of replacing existing decking or flat roof replacement cost per sf?

If you are doing buy and hold then compensating a high flat fee amount might be more appropriate.

Flat roof?