It doesn't take years. It depends on if you want to fly for hire, (commercial rated pilot). or if you want to fly commercial airlines, therefore an ATP pilots license is required. ATP stands for Airline Transport Pilot. An ATP license requires 1500 hours. A commercial pilot's license requires 250. (this license allows you to fly for hire) Basically, you can be a cropduster, banner tow pilot, fly cargo, etc.
=============
Aviation Schools