Investor returns

What is a common structure for the return of capital to a private investor after an acquisition?

I have an investor who is interested in giving me 20% of the purchase price I require to close my first transaction and he's asked me to suggest some terms. He said that he wants 50% of the company's equity but is open to other terms regarding returning his capital.

Should all the cash distributions go to paying him back for his 20% before I receive any distributions? Or would that be too much? What would a fair return be?

Thank you.