I think Family is the key negative others are mainly saying here... I wouldn't work with any family , but have with lots of business associates/friends.
If you are both business men, it could work well. Sure, partnerships can end poorly, but I have made a lot of money with people over the years.
Set expectations of who does what and how much and when /how each person gets out. If you are both reasonable dudes, it will work fine.
If either one of you has issues/addictions/etc, then best to stay solo.
I would set up a bond style of investment, where lets say he gets 25% back on his money in X years (or whatever you decide on). I wouldn't give him much more than 25% because you are doing all the work.
He invests 100K for example, you pay him 125 over X years.
I like the 5 year plans with a grace period of so many months when you get started for lead time.
The payment back would be about $2,100 a month for 5 years for 100K including the interest back to him.