Not sure if anyone answered you yet, but if I were you, I'd start with a 250. It seems silly, but you learn so much more starting that way. I started with a 1985 Honda Rebel 250, and the year after I got a 1986 Honda Shadow 500 (that used to be my dads). I was able to use everything I learned on the smaller bike, plus I felt way more comfortable. This summer I really want to get a CBR600, but that will only happen if I can sell the bike I have.