I don't disagree with what's fair, just saying that if you have a non 50/50 arrangement then you are probably going to have a different sense of when it's time

I don't disagree with what's fair, just saying that if you have a non 50/50 arrangement then you are probably going to have a different sense of when it's time to cash out than he is. Why not just make him your first employee and compensate him with incentive stock options? He would not be a partner or a founder, but a fairly large potential shareholder if things go well.