i started off on a brand spankin new bike with 0 miles and had no issues. id definately recommend getting a 600 or 750.

dont waste your time with the 250s and 500s. you will grow out of it in no time and the resale value sucks.

all bikes are dangerous, they can all go fast enough to kill you, the only difference is that the higher CC bikes get there faster. respect the roads and the bike and you should be fine on any CC bike.