(simple interest)72/7.2=10 compounds (years in this case)But if you got a lower interest, say, 3.6%, it would take 20 years for the same 50k to cost 100K. 72/3.6=20Now the numbers are not "hard" or "exact" but they are fast...And when your using money manipulation when negotiating, odds are that the other guy doesnt understand the value of compounding, atleast the way you do now.

Not all cases but lenders have a chip on their shoulder because you don't fit into a little box with a pretty bow for them.I often think it's comical when a lender see more strength in a Wal-Mart worker pulling down 10 bucks an hour than a business owner making huge bank with cash enough to pay the mortgage for years.

Say you make 20% compounded and double your money in about 4 years. 

Go ahead and sing one round of kumbaya for every layer of insane risk the OP is asking about, then triple it because the problems he will face compound exponentially. 

The remaining unused funds becomes your "Seed Money", and moves into...Level #2 - Compound your "Seed Money".  

If this were the case, then you'd need to see if/how the interest is compounded to know exactly how much would be paid back.  

That will get you to where you want to be.Read the Compound Effect.  

If you're able to save a good chunk of cash each year, keep the retirement savings going and take advantage of that compound effect.  

They can also offer less stringent qualifying criteria and down payment allowances.That doesn't mean the seller must or should bow to a buyer's every whim.

I was going to mention that that price seemed very steep for a non-specialty contractor, and paying on an hourly basis was a major red flag, but I think I now understand.You're already in a potentially bad spot having a family member owe you money, but getting into a contractor arrangement to pay it off could just be compounded issues.That said, to answer your question, I'd hire the guy exactly like you would with any other contractor -- Scope of Work, Independent Contractor Agreement, Lien Waivers, Payment Schedule, W9, etc. -- and pay him like you would any other contractor.