I had a Katana 600 as my second bike.
On a positive side, it's not going to power wheelie on you, but it's plenty fast enough to get you in trouble. I still managed to spin the rear tire pulling on the road once(was either cold, or hit some oil I didn't see). It'll hit 0-60 in about 4 seconds flat, which is slow compared to a modern 600, but still exotic car fast. And it's a pretty damn comfortable bike.
Negative side, which may be tough to get used to as a first bike, is it's a pretty heavy sportbike. Slow maneuvers can be tricky if you're just starting out. At least it's an older bike where you probably won't mind so much dumping it.
So it's not that bad for a first bike. If you have to go 600cc, it's what a lot of people would recommend, which is go for an older model like the Katana(not as powerful and sensitive as the newer model supersports). However you still may become a better rider faster on a smaller lighter bike you can really flick around...such as the Ninja 500, Suzuki GS500(if you really don't want a 250).
Just remember the whole "don't want to spend the money starting small then selling" is a weak excuse. You can almost always resell a used beginner's bike for what you pay for it(or close). Just want to point that out.
Have you ridden a motorcyle at all??? You may want to take the MSF first if you've never ridden, just to see how you feel on a motorycle. If you feel confident right away and do well, excellent. If you're very shaky, than you may want to consider a lighter bike.