I am looking into the same thing.... Talk with your local extension office. There is a commercial applicators license, a certificate of insurance of $50,000 for property and a $50,000 for public liability. Then there is a applicator certification. It is a test that must be taken. Your local extension office will have the study guide. If you want turf only the test you need to take is 3T, if you want to apply for bushes and others, you need to take the test 3OT. Cost wise, the certs are $30/year or $75/3 years plus $25/year for business license.
This is what was explained over the phone from my county office. They are sending me a packet with further information. You can call your local county pestiside office and they can give you your local restrictions