To be honest, that sounds like an accident waiting to happen, for both parties. Who owns the work you produce? Verbal agreements on this are great until push comes to shove. If the company exits, you'll almost certainly get nothing, regardless of what the founders have verbally promised. (not that the company should pass due diligence if the copyright status of their code is murky, but who knows)
And to answer, of course, especially if you're young and inexperienced, who knows maybe it'll work out, and if not, it's another app in your resumé.