First, thanks to everyone for their advice. I'm reading carefully.
Replying to your comment: yes, I think he is a good guy. But in all honesty, I would like to finish the product and stop working on it while holding to some (even small) equity in case the company succeeds.
We've already outlined a plan to bring paid developers onboard. Once it materializes, I would like to do less and less until completely detached.
It all started as a good idea and I had a lot of fun building it. Looking back, I see the quality of our current product and the time I've spent on it, and I think I should own part of it even if I don't continue to be involved in its potential success.