[z-factor]

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.

[snaveint]

In hmexx's scenario, once the MVP is ready, the developer has received the full amount of cash which is likely the main incentive.

In your proposition, the main incentive is your coding ability.

The key difference is that in the first scenario, the cash is a measurable benefit. In your scenario, your coding ability is uncertain, it could be worth more or less than the cash you are requesting - it's hardly worth gambling 50% equity on ones self-proclaimed ability.

[z-factor]

I think hmexx did not intend the money to be the major incentive. It seems to me that the major incentive there is seeing your idea finally implemented and having someone handle the part that you don't like or don't know how to do. However, as much as my ability is unknown from just this offer, I don't think it can be argued that it's any less than hmexx's marketing abilities -- he claims to be techie, not some hotshot marketeer.