There's no exact rule but I'd say 12 to 16 months is a good time to expect some sort of positive trend. I don't do any of that MVP stuff and go full-blown right away because user expecations are high and I'm too old to get pleasure from starting something out of a notion-hosted website. Cash-wise I try to keep it under 20k - keeping in mind that I don't do physical projects and all by myself (no freelancers, contractors, etc).