Yes. Airline pilots are required to have AT LEAST their Commercial Pilots license (to be an airline Captain you need to have one higher of a license called the ATP -- Airline Transport Pilot Certificate). You will only requre the Commercial license to START an airline career.
That said you must obtain a Commercial Pilot's license to be paid by someone to fly an airplane. So if you are a charter pilot, or a corporate you are a commercial pilot. That could account for the salary differences you see. That said, a First Officer (Copilot) during your first year with a major airline will make WAY LESS money than a captain who has been with that airline for 20 years. Also, a corporate pilot flying a private jet for a big company like Coca Cola or Wal-Mart will probably make a lot more money than a corporate pilot flying for Uncle Bob.
As far as training, it depends on what you want to become. If you want to go to the airline, you will need at least your Commercial Multi-Engine Pilot's license with an Instrument rating. To be competitive to be hired you will probably need a total of 600 hours flight time of which 100 hours will be in a multi-engine airplane. Depending on your path, that can cost $25,000 and up total.
I'm an airline pilot now and started out in the Air Force (not as a pilot though -- that didn't work out for me). Feel free to email me and ask any questions (I'm also a Flight Instructor). Too much info to provide here......