You need alot of time and alot of money, and I don't mean Pay For Training. Someone here can explain PFT better then I, but the bottom line is you end up working for peanuts or sometimes you even PAY to be in the right seat getting hours. That tends to make professional pilots angry because you are basically in the right seat because you have money and not because you have experience. You are taking a job away from someone that deserves it more.
Start of at you local FBO and try to add up all the costs of getting a commercial or CFII. It will take quite a while to get all the tests and flight checks done. Then you can start instructing or banner towing and building hours. You'll need a minimum of 500 hours and prehaps some multi-engine time, about 2 years of flying, before you can apply for something like small freight, or right seat in a small pax operation.
Then you build hours and move up to regional or corperate jets, then on to the majors if you want, which by the time you do all the above, hopefully have stabilized.
If you truly like where you are at any time, stay there and move up within that company.
This is one method of many. For as many pilots as they are there are as many different ways to become a pro pilot.
Good luck, and hope you're young.