You do not need to go to school for it. Just have a decent command of the language and knowledge of the subject. I do not know if you have to limit yourself to, say, sports betting. But if you do find a niche that you can get into that is okay, just do not let it limit you at the beginning, until you decide to specialize.
I know a few guys that do exactly this. I know a guy that specializes just in NCAA football and one that specializes in horses. I know a few more that are all over the place. Only one of them does it as his full-time thing, but he is retired already. Blogs are a nice way to get started and make a name for yourself. Then you will have some material to present to a local paper or news site. Then maybe you can cover a local sporting event for them, etc.
However, the main thing that guys are doing nowadays, besides blogs, are podcasts or YouTube channels and that sort of thing. These are guys that are younger and trying to generate sources of revenue to make a living from something they love. I know a few that this is their sole source of income.
I know folks that do this for a living with travel and poker, for example.
This, of course, is not writing, alone. So, you would have to have/obtain a couple of other skills, like public speaking and videoing, etc. But they are easily learned.
So, there are many ways to do this, even if you want to concentrate on sports-writing.
There are many places on the internet that will actually walk you through some of this.
I think some of the job recruiting sites also have postings for sports bloggers.
There are forums of all types online. I do not know for sure if there is one exactly for what you want to do, but there might be. I would look and see and, if so, maybe you can connect with someone that can really help you get started.
At any rate, keep us posted with how it goes. And good luck.