What's wrong with buying a new bike in a year or so? Guess what? Not matter WHAT you buy, you'll be itching to step up to something nicer in a year or two.
Start off with a Ninja 250, Ninja 500, or even check out the new Suzuki GS500. They're plenty quick enough, but more forgiving than a 600 sport bike. Because they're lighter and more "flickable," you'll build confidence on them faster than a bigger bike.
Also, the market for used 250/500's is huge, you'll sell that bike in a matter of days.
Anyway, welcome to the forum, there's a lot of good info here, and good luck.