Generally speaking, pre-fab homes come with existing HVAC and Electrical systems, flooring, insulation, etc. and some brands even promise they will meet the specs for the local building codes anywhere on the continental U.S. 

Isn't finished out with sheetrock or anything either, just basic plywood...may or may not be insulated.  

Electrical, plumbing, insulation, drywall, flooring, kitchens, and baths will be completed by myself.  

All the insulation loose in the basement I could put back up myself, unless that's extra insulation that's just sitting there. 

I must have gone through 30 cans of fireblock foam before the insulation inspector left me alone.  

It does not matter that you plan to sell in 5-7 years, you need to get into the market as soon as you reasonably can to fix your cost of living and insulate yourself from (and benefit from) long term appreciation in price and rent increases.

Insulation needs a permit....roof replacement needs a permit...etc.Jurisdictions are different, but if you own the home in an LLC and you are technically not the homeowner (the business is) then you cannot pull a permit yourself unless you are a contractor....this can get a little sticky depending on where you are doing the work.  

Or barring that possibility, a way to use financing while insulating our credit from each other so that if the worst happens, my friend disappears, and I can't cover her share, I'm not totally screwed? 

All,I have a rat problem that has been in one of my houses for awhile, unknown to me and I have to get it cleaned up.One company I'm working with says I need to remove all the insulation, droppings, clean and treat and reinstall new insulation.

Insulation can hold a smoke odor.