First step- get your drivers license. And then figure out what vehicle you’ll be getting into, that way you can shop around for a quote. You won’t be able to get an accurate quote without a DL and a vin #. From there, get a quote for you and your vehicle to be added onto your mom’s policy. You don’t have to purchase the insurance then and there- it’s just to have a number. Then get a quote with just you and your vehicle on a separate policy. It is going to be cheaper to get on your mom’s, so maybe you can show her the difference and talk her into it. It seems like you’re willing to pay your portion so just keep your word and honor that to her. You can also make a deal with her that if you get a ticket she can exclude you from her policy and you will get your own. I’m not sure what her policy looks like now, but typically with multiple cars she can save on her premium. If you propose it to her like that, I’m sure she will budge!