Same as almost every other career in the medical profession - 4 years of undergrad, 4 years of medical school and then at least 3 years of residency. And that doesn’t mean proving that you’ve lived in the state of California for the past 3 years. You will be almost 30 before you make your first dollar and likely have a bunch of debt.
Also, as you’re dealing with a lot of families, it’s especially important to have a heart of gold. Just knowing your stuff is not enough - you have to make people feel better about their physical condition, even when you know there isn’t much to feel better about. In that sense, you’re almost like a paid actor, which might be a difficult concept to wrap your head around.