A 250. I would say first let him ride a dirt bike or something small just to get the feel for it. I would stick a 18 year old kid that has never ridden before on a 600, and your an idiot if you stick him on a 1000. Might as well pick out his coffin also. 250 is the way to go, and a good leather jacket and helmet.
Even a 600cc sportbike is too much for a first time rider. Especially with being as young as you are. Needless to say anything about a liter bike.
Motorcycling inherently dangerous, and the kids like you who want to hop onto liter bikes straight off are the ones who die from it. A bike is not a penis extension. Having an R1,1000cc Gixxer, ZX14, or a Hayabusa doesnt make you cool, and to be honest, they really have too much power for anyone. Are you planning on racing? If not then why would you ever need something that can do 187mph?
Start slow if you plan on riding. Take an MSF course. Get a 250 Ninja, or something similar. Learn how to ride, and maybe move up from there.
If you want something with great handling then why buy a liter bike? the bigger the engine the heavier it will be, meaning it takes longer to tip it into a corner, if you want great handling then buy a scooter; but i get the impression that you actually mean "i want great speed" in which case find a bridge and use it because that will be then end result of any 600cc+ bike.
In the UK riders are restricted if they are under 21, this restriction is to 33hp, (a gsxr1000 is about 180bhp)My bike is restricted it still does 0-60 in 6 seconds ish, have you ever done 0-60 in 6 seconds when your in control of the vehicle? no i didn't think so.
A gsxr 1000 will do this in around 3 seconds so i doubt you could hold on any way...
Another example of why its too quick for you is... i once heard a story of some one with a big bore bike who went for an over take but put the power on too early and hit the car in front and died, he was experienced (all it takes is a small lapse in concentration)