Then I think you MUST be listed as at least a driver, in which case you can only drive THAT vehicle. Another alternative is if y'all have several cars, you can skip individual insuring and get an "umbrella policy." This basically covers all listed persons on all vehicles on one policy if you set it up right.
Do not make yourself the primary driver, then you'll be broke for sure
. It's usually cheapest to have your mother/female as primary, and you as a driver.
I'm 24 now and have a '67 Camaro with a 383 and, as primary, I pay about $360/mth. When I was 18, my mother was listed as primary and I as a driver. My premium was $66/mth and hers was $76/mth. So, I paid both ($142/mth) and had cheap insurance. And, NO!, she NEVER even sat in my car.
I'm just skipping stones...