Well the first thing I can tell you about shooting sports is that unless you are really good and even then, you won't be travelling the world shooting sports. You won't be making 100k per year shooting sports, most likely you end up less than half that. You're looking at spending between $25-35 thousand on gear. The majority of the photographers that cover the Olympics are working with agencies and they are supplied with the gear, many don't even own their own gear. It's not as glamorous as it seems. I've covered eight Olympics, and for the most part it's 20 hour days, up at 5am, on a bus and then sitting at a venue waiting eight hours for a race to start, no leaving the spot or you lose it, you pee where you are, go without food, and then wait some more. This is just a simple example. I've been shooting swimming for the past two weeks, up at 7am, the pool by 8:30, a two hour break inthe afternoon to work on the pictures, then back to the pool for another three hours of finals, and then back to working on the pictures for a few more hours. I could keep going on.
If you really want to do it, you'll have to start small, shoot as much sports as you can, different sports, even if you aren't selling stuff, you'll get an idea of what is involved. It's never easy. I've been shooting sports for decades, and it gets more difficult all the time, not the sports themselves, and I don't have trouble producing high quality images, it is becoming filled with the getty fast food garbage producing photographers where only the handfull of guys at the top are the ones that work the big events, all the little grunts end up shooting little league events for $50 a day.