I have a 04 CBR 600 F4i. It's a good, reliable bike. Biggest thing with most sport bikes is make sure you check that it hasn't been beat. Make sure it hasn't bounced down the road in a wreck.
Look at the handlebars, they should be good and straight with the front wheel, if they aren't it probably isn't a bike you want. Sometimes it's good to check the head bearings too. If there is play, it's probably been stunted a bunch.
Otherwise, the CBR is a great bike. May be a little fast for a bigginner, but if you are smarter than your wrist, you'll be fine. Keep in mind, a street bike is entirely different than a dirt bike.