Short of tearing down the downstairs ceilings and installing soundproofing materials, there's nothing I can do.

@Clara Brashear,Hi Clara,I assume you mean how to be your own General Contractor hiring/managing/paying subs on your own work site and not swinging a hammer yourself.Going to work for some one else in this field would probably take several years to figure out all that needs to be done.For instance, material and labor lien releases, payment schedules that CYA, interim and final work inspections, etc... 

I purchase, he fixes it up at discounted rates and no mark up on materials, and we split the profits.

I'd also recommend that you start finding a very knowledgeable and wholesale friendly real estate attorney that will be able to review and approve your purchase agreements, marketing materials, and general business practices allowed by your state.

Turn key companies have significant advantages over individuals. 1) They buy further upstream at much better prices, 2) they generally get substantial discounts on materials through economies of scale, 3) are better able to control their labor costs by using the same crews regularly, Ask yourself if you really want to take on all the risk on the off chance that you will really save much money if any at all.

The inside is a complete mess, demo materials scattered all over the place and all kinds of stuff that I’m sure he intends to leave.

Not including returns figure about 100 including material excluding finish work.400 sq ft per ton = 3 ton 3.5 if really old home.Can panel hold new load?

If all the trim in the house has lead paint, removing and replacing all that trim is quite a bit of work/materials.

They did tell me the original siding material they got didn’t fit, they were too thick to fit underneath the original siding, so they went with weathershield 2x contact boards and used dog ear wood for the small connecting pieces.

The materials, and work done by subcontractors, 80k.