I'm retired from work now and one of my 'jobs' is doing sport for an agency on a commission basis. Mainly Premier League in the winter and top class cricket/tennis in the summer. I've made a lot of good friends over the years among similarly minded people who love sport and love photography. We're commonly referred to by some full-time rs as 'Muppets' or weekend warriors.
We've all paid our dues in the lower leagues and we're all decent togs whose work is published nationally and internationally, mainly via Getty or Rex.
There have been people like us at the margins of sports photography for many years - my own experiences goes back to the late 70s when most togs at top flight games worked for a paper with a few 'freelances' alongside. The old technology of film and having to physically deliver prints acted as a real barrier to anyone trying to 'make it' in sports or editorial photography.
Technology, of course, has transformed the equipment we use and gives anyone with half decent gear the chance to produce images of comparable or equal quality to full-time togs. The problem we all face is how best to distribute those images widely and quickly, especially when the guy sat next to you is transmitting straight out of the camera to his agency and doesn't even have to bother with a laptop. Distribution was an issue back in the pre-digital days, too.
We all would love to make more money out of what we do but the reality is that the money is spread very thinly and most of us are totally reliant on our agencies to get our pics distributed widely and relatively quickly. In the meantime, we do what we do because we love it. If I could find a way of making more money out of sports photography - and much of that seems to depend on where you live and what your local circumstances are - I would go down that route as well. We all make our own choices about what we do and why we do it, so good luck to anyone who can do this stuff well, enjoy the act of doing it and who can make a few bob along the way.