It's so hard to hire a co founder who would just work for equity.

That's because you're trying to hire a cofounder

I've had many clients approach me and propose the idea of me building their idea and getting a share of the profit instead of an hourly or fixed price. So far I have turned them all down, if I don't believe the idea will succeed, there's no way I can invest that kind of time. What people don't seem to get is, for a developer there is a massive opportunity cost to developing without being paid. If your idea is great, you should be able to get funding through a bank or venture capital firm. If you do that, you can pay your 'co-founders.'

I've actually taken on a few of the ideas friends have pitched me. I was naive, and as others have said, a huge time sink. I'd never do it again unless it was my own idea. I know that the other people (business development, design, marketing) think they're contributing the same amount of effort, but they really aren't.