You are opening up a new market in partnership with this guy. He is putting his compensation on the line. The new market is a gamble, he is, in effect, betting his compensation on the future outcome of the business.
What are you betting?
The bets will continue until the market becomes profitable. You have no way of knowing, for sure, when this will happen.
So, rather than guess
the split (10/90) use the bets to caculcate the split using the Slicing Pie model
. Slicing Pie is a formula for determining the right equity split based on the relative fair market value of the contributions of time, money, ideas or any other contributions that are unpaid. It is the only fair way to solve this problem. ALL other methods are guesses (at best).