[davetong]

An idea without execution isn't worth anything.

You'll be doing all the work up front and then all the work maintaining and improving.

You're also not a flight risk as it sounds like you're in it for the long haul.

They also sound like they're not convinced, which means they either haven't though it through or they're not worth the risk.

Good luck with the decision. I would vote a no for them as it sounds like you deserve better and if you keep looking, you'll find some cofounders worth taking the startup risk with.