you are pissing money away on a ninja 250. the power will be terrible and you will regret spending the money on it. my friend got one about 2 months before his 16th birthday, he sold the bike about a month and a half later and bought a gsxr 600.

ive ridden a few 600's (r6, gsxr 600) the power is very easily delivered, then i jumped on a 2009 r1 and that would be a terrible beginner bike. theirs to much power on the lower end for a new rider with no experience. i highly recommend test riding a bike or two before you waste money onto a ninja 250.

a 650 is not that big as i think your imagining and in the end, if thats what you want you will be much happier