I did it all in about 2-3 years. I was a big collector as a kid but didn't get back into it in a serious way until 2021. Becoming an authorized dealer is basically, fundamentally about building trust. The whole coin industry operates in a very old-school relationship-based trusted way. To become a member of most professional orgs or become an authorized dealer, you need to have 5-10 VERY solid references from other members or authorized dealers, and the only way to get those references is to be a part of the community, build trust, and build relationships by doing business with others (which means honoring your commitments and your word and writing good checks, etc.). In the end, you need to ask 5-10 people to personally vouch for you, so they'd better know you and actually trust you.