Get an affordable bike first, you will most likely have a few '0mph' tipovers, and it will be entirely yours to mess up.
My parents were not thrilled to say the least, but everything for the bike has come out of my pockets. Except for the MSF class, which my parents were willing to pay part of, as my dad and I have done several track schools, and have become better drivers because of them.
Just go for it with your own money, and deal with any problems yourself, they will complain less. Like earlier this week, my bike quit running halfway between home and school, so I let them know after I had arranged to drop the bike at one friend's house, and have another friend pick me up on his way to school. BTW, I just went and got it today.
