Licences required to operate machinery changes depending on the machine and state/province in which the renter works. These requirement can also vary depending on the machine in question.
Operators should never rent or use equipment that they do not know how to use safely. If you are being asked to operate a machine for your job, you are completely in your rights to ask for training on the machine.
For information on what licences are required in your state, visit the website for your location or local government.