When you're teaming up with a cofounder, you're not just getting a free employee. You're getting a business partner, and that person needs to be someone who complements your skills. But too often, I see MBA types who are "looking for technical cofounder for lots of equity" to mean "need a code-monkey who I will boss around for free."
Even more distressing is the fact that so many young programmers will go along with it.
If we're going to be cofounders--and let's just assume for a minute that I have the technical part covered--then that means I expect you to be able to prove that you know how to perform the tasks of marketing and sales. I can show you several past projects I've worked on. What can you show me?
And you need to be putting in just as much effort on your job as I'm putting in on mine. And no, you are not waiting for me to finish the product. That's not how marketing works. You need to start now.
Nobody has managed to do that yet--and there have been several suitors--thus I haven't taken on a cofounder.