What percent return should we pay our money lender?

[Kelly Natkie]

We have a friend that wants to lend us the money to help us buy a fixer upper that we want to live in for 2 years and then sell.  We would be able to pay him back once our current house sells and we can move into the new one once renovated.  So, we would probably have his money tied up for 4-5 months.  It would be around $250,000 that we would be borrowing.  What is a fair amount of interest to pay him?