The biggest problem I have with getting an offer to be a technical co-founder is that if this person's main interest is in business, why are the not already rich? A developer's main area of focus is not money so they are less apt to accumulate much, but if your central focus in life is business, then I can't really have a good feeling about your skills if you are not currently rich or have built a successful company. It's like saying you are a great developer but you don't have any software or code to show for it.