Quitting your day-job, sitting in a co-op space, risking thousands of personal funds, building, and building, and building, and building, and then finally releasing something with no real idea of it's potential is an almost sure-fire way of failing, and risking your well being at the same time.
This "prove-everything-at-each-step" side hustle method is how most businesses should be started.
Take notes, well done.
These days I wouldn't do that, because I have a kid and a mortgage, but I don't regret doing it at 19 - it taught me a hell of a lot of things that I'm not sure I would have if I'd only tried the cautious approach, and it still I think affects how I do things (e.g. it taught me that as much as testing and validating is important, sometimes it's better to just dive in, try, and fail fast - which is right depends how much you're risking and for what; you just need to actually assess your risks first).