Let's talk about a) only. It depends on who this cofounder is and what role he is going to play. Does he have a narrow skill or market experience that is usefu

Let's talk about a) only. It depends on who this cofounder is and what role he is going to play. Does he have a narrow skill or market experience that is useful for a specific idea? Then post-idea. Is this someone with whom you've had rapport for a long time and many times said "hmm, it would be nice if we worked together on something"? Then pre-idea.