Bottom Line: There is a big difference between paying someone nothing ongoing and paying them even a small amount. The other answer where they were paid only $18,000 is still very different than no ongoing pay.

When you ask someone to commit their time and talent with no guaranteed return you'd better have a pretty convincing reason. what if your product doesn't work? What if you change your mind?

Many experienced entrepreneurs will advise people to never work for free, especially bus dev, and I would usually agree.

One option is to give them some equity up front, show that you're willing to take a risk. It would force you to choose wisely and treat them with more respect.