I'm developing a web-application for an active shooter defense training company. They go to organizations all around the country and teach them how to be best prepared for a horrible unexpected event. They want to take their training program online to reach more people.
I've been actively working on this for a couple months now and a friend of mine started helping me. He was very motivated at first, but his effort has started to die off.
I can't pay him because I don't make any money until after the application has been developed and deployed. Anyone working on it (including myself) are pretty much volunteers. Once I start producing income, I can pay him. But, I don't expect to be able to do that until last quarter 2019 or first quarter 2020.
I've come to a deal with him that once I start creating income, he'll receive 10% of it up to 100k per year. I originally got him motivated by the technology we'd be using, the fact that he could work on the fully technology stack, and the cause behind why the application needs to be created.
How can I keep him motivated while he's basically volunteering his time for me during these "startup" phases?