Man, listen you are about to do a mistake. If you start a sport you gotta actually compete in it. Boxing training, generally, is really healthy and if you keep it up for a couple of years it will be great for you in the long term. Now, the thing is with boxing, is the boxing part. I don't know how old you are or what kind of physical abilites you got but if you're about to start boxing in your late tens THEY WILL BEAT THE FUCK OUT OF YOU. And if you're into it, it's okay with me, but I'm saying if you are so concerned about your long term health problems boxing is not the sport for you. There are many WAY more efficient ways to train healty, individually or as a team. And by the way, the ignorace of you not knowing famous athletes in other sports is your problem.
TLDR: its bad long term (look at tate :balding in early twenties), and you are ignorant if you don't know other famous athletes (Messi, Ronaldo, Nadal, you get the point)