my gut is that you make him a co-founder with a strict (and very clear-get lawyer help!) vesting schedule he also needs to have skin in the game, which means a

my gut is that you make him a co-founder with a strict (and very clear-get lawyer help!) vesting schedule he also needs to have skin in the game, which means a monetary investment if you have invested monetarily, and he needs to be full-time if you are full-time (as I hope you are!)