Actually, since your doing a form of possible ride sharing you might be subject to the beefy insurance regulations found here
If you need that policy, it starts at 50k!
Local transport companies are subject to different regulations but are required to carry by law in CA:
Work comp for driver
Vehicle insurance including liability, accident, and possibly physical damage.
I can help for a reduced fee if you have additional questions on this topic as we are also compensated by the insurance companies for the policy placement.