>>1197539>>1197540This, times infinity.
You have to start at the bottom like everyone else and work your way up to Cat-1 or Cat-2. Then you don't 'apply to a pro team', you're scouted by a pro team who will approach *you* (or not), just like any other professional sport.
The only thing different I'd say from the dude I quoted is you don't have to win 'every race', you only have to win *some* races, and earn enough upgrade points to upgrade from Cat-4 through to Cat-1/2 (preferably Cat-1) and then be able to declare yourself Pro and hold your own well enough in the Cat-1/2 Pro races to distinguish yourself and get noticed by the scouts.
Along the way you're going to be on one or more amateur-level teams, starting with development teams, because you're not going to learn everything you need to learn in a vacuum, you're going to need to learn to work as part of a team. None of this is fast, you'll be spending many hours per week training, getting up at wee hours of the morning for races, endure crashing and having to spend time healing, and as obsessively pursuing your goal of becoming a pro rider as any other athlete does -- and in the end you may not make it, you may not have what it takes physiologically or mentally, may stall out at Cat-3 (or never make it out of Cat-4). In short: don't quit school for this, even if you make it as a pro rider at some point you'll burn out and won't be able to cut it anymore and will need some other life-skills to fall back on so you're not working at McDonalds the rest of your life.