The only time I've been left owing bills was when it my was gig. I'm not sure I'd be willing to come in to a situation with someone else where I'm signing my name to something where I'm in a position to be personally responsible. Why is the other person (the original founder) not being required to pay on the debt?

Maybe you're meaning something else by 'paying their bills' - do you have some example(s) you can share?