Sounds like you basically want to run a co-op. That can work for some kind of businesses, but I hope you have the funds to build and launch the product out of pocket or have rich friends willing to donate money for free because they believe in your cause.
There isn’t enough info here to meaningfully answer your question. If he’s experienced in the industry and already has customers interested in a hard to penetrate B2B market, and the product is something any competent developer could build, 23% might be very generous. If it’s a highly complex tech product that you have some unique qualifications to build it could be a rip-off.
No way to tell without more details.