First of all the same problem exists with hmexx offer -- he can stop putting any work in and will still be the 50% equity cofounder.

Second, if the business is promising and I have a significant equity in it, of course I'll pour more work into it. I'm on the next project only while the other party does their part marketing until we evaluate in a couple months if it's working out.

And I also want to point out that my work is not something you can buy on elance at all, and most definitely not for cheap anywhere.