If you want to be able to make money as a pilot, you need to have a Commercial Pilot Certificate. It's not just for airline pilots - even a crop duster needs a commercial license! Commercial pilot training enhances your ability to control the airplane by executing specific maneuvers to very high standards. You must have at least 250 hours of total flight time to obtain this certificate, and there are other requirements which include:

Prerequisite: Private Pilot's License

Age: 17 Years

Total Flight Time: 250 Hours

Commercial Instruction Flight Time: 20 Hours

Complex Aircraft Flight Time: 10 Hours

Third-Class FAA Medical (To Obtain Commercial License)

Second-Class FAA Medical (To Excercise Commercial Privileges)

FAA Written Test

FAA Practical Test (Checkride)

For further reading on the FAA requirements for a Commercial Pilot Certificate, you can check out CFR §61.121-133.