Peter Jackson is the 3rd highest grossing film director of all time. He is an absolute legend, but he got his start following the same pattern that all best filmmakers do.
He made movies for fun with his friends. They wore all the hats and played all the roles. They DIY-ed their own gear/props/costumes as they went. They broke all the "rules." They kept their day jobs. They made their first feature film in their spare time. They had no formal training, but lots of fun. And the rest is history.
Documentary about the making of Bad Taste
Free "Make Your Feature Film" Checklist