I met this guy who became a game dev later in life, as in his 30s. He has quite the non-traditional resume as far as devs go, with no formal CS education.

In any case, he went on to work on a game, and kept doing so for years. He hired artists etc. but did the core development himself. Released the game, which has now sold over 150k copies since the release last year. Obviously not crazy numbers up in the millions or tens of millions, but impressive for a first release, and from a dev basically learning as he's moving along, with a regular 9-5 job and family - doing it purely for the love of the game.

Makes me wonder if he'd ever have gotten the chance, had he first tried to join some small indie studio, rather than the DIY route.