It takes more than just an interest in history to become an historian, which means that even though your Uncle Leo gets riled up about the Revolutionary War (for whatever reason), he is not an historian. An historian is someone who is recognized as an authority on history.
To become an authority, you must spend your fair share of time in school. Budding historians generally get their bachelor degree in history or art history. If you want to sit out graduate school, you can earn an Advanced Certificate in Public History, an Architectural History certificate, or a Museum Studies certificate. Certificate programs focus on teaching you skills that you'll need on the job. They typically take around ten months to a year to complete.
To make some dough or just get a better jump on the job market, you must attend graduate school. There you will learn all about how to properly research history. Those who want to get a job at a museum may take some art or museum studies or art classes.
Once out of graduate school, your plight may not be over. A lot of historians earn their Ph.D so that they can get a job at a university. Furthermore, a lot of historical consulting firms, government agencies, and museums require that their applicants have a Ph.D.
Why? Nowadays, employers can ask for the moon. The job market is so saturated with people who have their master's or Ph.D that competition is fierce. It's like a tiger at a barbeque, and it won't let up anytime soon, because people continue to go the graduate school route.