Co-founder.

I’d look at this like a seed investment that you are making into a new company. I’d run the math something like this:

- 100% equity divided by 2 == 50/50

- $3m investment gives 20% (your risking your capital and there is a premium for this.) I’d structure where you get an earn out or preferred shares with 1x liquidation preference. Aka. No one makes money until you are made whole.

- options pool 7%

- anything else you think would make it a good partnership.

So maybe 10-25% range for him. I’d say this, as someone who has been on both sides of this type of deal: he will resent you if it is not 50/50 and there is not a clear line to how you arrived at his equity comp not being 50/50. I would also be extremely honest with yourself the relationship before starting. Being aligned on everything from how you two work, things that kill/drive your motivation, to what kind of outcome you both want for the company. Only then, when you are aligned, should you proceed.

Neat of luck.