Business co-founder's equity

The role of the individual doesn't matter as much as a) their level of contribution (typically in time and/or skill) and b) how critical they are to succeed.

If you only had the idea and couldn't launch the business without them, then they are an equal partner. If you had already built the product and were looking for them to join you to take it to market, then perhaps it's a smaller share.

Unfortunately there's no set rule for this - it's really up to you and your partner to determine what you feel comfortable with.

A couple of ideas worth considering, though:

1) If you're asking because you're worried about them walking away from the deal and taking shares with them, you could consider setting things up such that they would gain increasing ownership over time.

2) If you're worried about being equitable, then something that's worked well for startups I've participated in, is to determine how much our time is worth, then track time, and issue shares to ourselves in lieu of money. So, if your time is worth $100/hr and you put in 2000 hours in the coming year, you may issue yourself $100 x 2000 = 200,000 shares. Likewise, if you determine that your partner's time is woth $150/hr (maybe they're more experienced?) and they only put in 1000 hours, then they would get 150,000 shares. Everytime we've done a variation on this approach, everyone has felt that it was very fair.

Hope that helps!

~Joseph

Joseph's answer is right on target. Just to emphasize something he said:

The role of the individual doesn't matter as much as a) their level of contribution (typically in time and/or skill) and b) how critical they are to succeed.

The fact that you are the technical co-founder and your partner is the business co-founder is totally irrelevant. These are just titles, that in most startups are meaningless, because you both have to do whatever it takes to make the business succeed. The main issue that matters when it comes down to splitting equity is how much time and effort each partner has (and will) put forth.

A hypothetical "toilet bowl cleaner" co-founder should be entitled to as much equity as a technical co-founder if they both put forth the same amount of work, and both duties are just as critical to the success of the company.

In your case, I would guess that both the technical aspects and the business aspects are equally vital to the success of your venture...you won't succeed without both pieces. Now all you have to decide is how much time each partner will put forth. Joseph has given you some good options for that.