When renting from Budget car rental service, do you need full insurance coverage?

I'd like to understand what kind of motor insurance do you want to get in most condition.

Simply liability?

"I live-in California and I am 16Auto insurance cheaper with 2 owners?

Do I need to have both insurance plan?

Is there insurance for Antique Cars?

"I am going to get insurance through State Farm and I wondered if I will must produce a down-payment around the insurance and when