Well I'm 36 and have been riding since I was 6, I had cr500 Honda motor cross bikes from 13 (think my parents wanted rid of me) and been road riding since I was 15 (I know to young for a license) I can honestly say tim get a off road bike and learn from there before you even contemplate a road bike as there is so much to learn about bike control, let alone riding defensively on the road, a good modern 600 is making 120bhp these days and will knock on the door of 170mph and they brake and excellerate at silly rates too....learn from the beginning mate and don't become another statistic.
I have lost a few friends on the way from very skilled racers and normal road riders and most are from getting over exited and it going wrong (one was decapitated )
My bike list I can remember there is more ,at one point between me and my brother and dad we had 16 bikes for road and track.
Dt175,cr125,cr250,kx250,rm250,cr480,cr500. X3,xr600r,gsxr400,zx6r,gsxr600, Harris mag1260,r1 David jefferies TT rep,zx10r gsxr1000 running nitrous etc,
And have also ridden zzr1100,gsxr750 srad (used to take my dads when I was 16),zx12r,hayabusa turbo,hayabusa,kwak original z1(I now own it),rg500,rd500,goldwing,