What I had in mind was having a builder handle foundation, framing, roofing,electrical, plumbing, etc.

The only thing they share is fire sprinklers and roof. 

I was able to find a few good subs like electrical, landscaping, roofing, AC tech, foundation, yet can't find a good general contractor. 

Roof, windows, landscaping, carpets, paint job.  

So, often times those are paid by the landlord and included in the rent (if they are flat fee) or possibly billed back to the tenant (if they are based on usage).

Any town near you look for a flat topped church or old elementary school for sale.  

, roofer to see if they are getting into the exhaust vent on the roof?

The last think you want to do is to put leverage on one of them and then need a new roof or furnace.

Its easy and cheap to insulate accessible locations like an attic and since heat rises and the sun beats down on your roof the attic insulation is probably your best bang for the buck when insulating.

Also remember it will take time to get them done, during which the home is vacant and not on the market.People shop with their eyes-so many don't care about stuff that is really important (plumbing, electrical, roof, etc).