Typically we just make sure the grey box is install properly but I personally have not had them installed or requested to be doing bank work or flips.

What is needed to complete:-Additional painting and touchup painting of walls, trim, and blinds-Repairs to oak wood flooring, plus sanding, sealing, and clear-coating the entire floor-Laying marble tile around a fireplace-Installing a sink in a granite countertop, including cutting the holes, etc.

What about people like an AC company who installed a new AC?

He has came to me and said they have money to make alterations to the house that would include installing a backup generator, ramp, shower, and a few other items.

I wouldn't go to the trouble of an installment contract for 1 month and legal title isn't conveyed.

In the early days, they did all the rehabbing THEMSELVES (installing new dishwashers, etc.) 

Wherever there's insulation installed, there's always a moisture barrier with it (if it's done per codes).

Even though I'm a CPA, I no longer practice tax nor have significant experience with this type of installment income.

Seller financing cannot charge points, the loan is funded by equity, and there is no pre-paid interest for equity under an installment contract.

You better off going with home depot install service.