The money would be completely for the startup. Of course there are many variables to consider in this dilemma, but I didn't want to make the post too long.

As for our roles in the startup, he is a web developer, I'm a mathematician/developer, so we complement each other. Just the two of us, at least for the coming couple of months. The idea that I'm getting, already in this phase of preparing for the startup, is this: in a startup, there's always work to be done and you get bonus points if you iterate fast. So that kind of mitigates the factor if somebody is a good multitasker or not (I'm more of a believer in focus).