To qualify for your commercial pilot license, you must have logged 250 hours of flight time with 100 of those hours in powered aircraft and 50 in airplanes. Also, 100 hours must be pilot-in-command, 50 of which had to have been in an airplane. You also must have logged 50 hours of cross-country (10 in an airplane), 20 hours of training (10 instrument, 10 complex or TAA), and 10 hours of solo training.
Basically, from PPL to CPL, it will take approximately 7-10 months to complete the training.