I did some geo-coding a while ago but anything large scale is going to be costly as all the APIs have non-trivial fees for > hobbiest usage. Have you asked any geo-coding companies for free access? I bookmarked this site a few days ago because I still have a few itches I'd scratch if it didn't cost me an arm and a leg ... it should give you some idea of what a large-scale deployment of your application would cost - https://getlon.lat/.

I'd be interested in helping with your effort but I think you should describe your architecture and technology choices a bit. How do I know if I'll fit in? (and if you want to launch quickly, now isn't the time to have engineers learning on-the-job).