I would look at it like convertible debt. The co-founder gets x percentage of the company now OR you can buy that equity down in the future once you get funded.

I would look at it like convertible debt. The co-founder gets x percentage of the company now OR you can buy that equity down in the future once you get funded. Keep it open so that if you work well together the co-founder can stick around and earn more equity. If you don't vibe, separate on previously agreed upon terms.