If, however, you are buying it with cash and without an inspection, you could tell the seller that you can close in a few days, which might let you negotiate for a lower purchase price.In the scenario where there is a loan with interest, and the interest is all your father-in-law receives (he isn't getting any of the profit after the sale), then he is indeed a true lender and this is a true loan/mortgage.

You might have to give part of your profit to a Partner but part of something is better than nothing. 

I plan to do this by reinvesting my profits into more properties and living off of our W2 paychecks.

At most you have $40k profit -long term capital gains at approx 20% tax is $8k - most likely worst case tax. 

Then go from there and use the flipping calculator to figure out how much you can offer and still make a profit.

., plus a satisfactory profit, then go for it

This allows you to isolate the single note to easily determine profit or loss.Separate QB files may have to be consolidated for tax purposes, but that should be far less frequently than reporting to JV partners.That’s my “solution”I hope it helps.

The outcome would be a sizable profit margin to split up between myself and the builder.

I would prefer getting fixed price bids from contractors because this will make evaluating profitability easier/faster.

Reach out to a few and find one who will take you under their wing.If you're feeling altruistic, another way to learn and get construction experience is to volunteer for non-profits like Habitat for Humanity.