I just failed my driving test...
Depends on your country and family. I was an occasional driver on my mom's car insurance plan for 5 years before getting my full license and buying my own car. If you're in a major city, it's bound to be terrible. I registered my vehicle in a suburb one of my parents live in. I pay $207 CAD/month, living in populous dense southern Ontario. Next year I'll be 25, so it'll drop even further from what it's at. Wayyyy better than other people I know.
Not sure how it works in most European countries, but in Canada it goes by provincial guidelines. In my province, we have a written G1 which you can complete as early as your 16th birthday, allowing you drive once passed with a full fledged G driver for practice. You can complete your G2 a year after that, and then your G within 5 years of completing your G2.