How can I buy a sportbike ate age 17? and how much will the insurence be?

I'm 17 and I want to buy a 2008 kawasaki ninja 250R ($3500) and I know I can afford the 80$ a month because I make $150 a week and I heard I need a co signer for a loan because I don't have credit but what else do I need to buy my bike ASAP?