Ask HN: How much is sweat equity worth?

I've been working on my start up by myself for nearly 2 years and there's been some interest from a handful of potential advertisers to finally start bringing me some revenue. I'm at the point where I can't do it all myself and need to bring on some partners. I've got well over 4,000 hours into this and over $25,000 personally invested but I still own 100% of nothing at this point. Can I even put a valuation on the company yet? How do I determine how much % to give to new partners?

My question is, if I bring on some partners how do I measure the amount of work required by them and for how long? Say I give a programmer 5% in return for 25 hours a week minimum to start with. How many weeks does he have to work to earn that 5%? And what happens when that time is up? He owns 5% but doesn't have to do anything more? I'm assuming if someone is invested in a business that much, they will work beyond the minimum...is that common? Perhaps a sliding scale would work in this case.

I plan on bringing in a couple people to take this to the next level and just want to know what I'm in for. I know this subject can go on for ages, but I'm hoping to get some insight from seasoned people.

Thanks!