Tie it to milestones and accomplishments and make sure you have an opt-out clause if the thing falls apart with nothing to show for your work.You do NOT want to

Tie it to milestones and accomplishments and make sure you have an opt-out clause if the thing falls apart with nothing to show for your work.You do NOT want to give permanent ownership of your labor in exchange for a loose promise to deliver the stars. As a fellow developer, I imagine you have worked on this for ages, and will likely continue to work on it even without them. It is important you avoid getting yourself put in a position where you cannot do that, or end up delivering IP to someone else to monetize. If selling your product ends up being more difficult than they think, will these bail and still demand compensation if YOU pick up the ball they drop and run with it? How serious are they and what signs are they giving you that they deserve equity at this point. If all they are doing is sales, you can set up a commission structure, and tie equity in your issues to the company's hitting successful sales milestones. If these guys want ownership to start, another approach is to license your existing codebase to the new venture. Be sure to get this license down in paper!