Sportbikes aren't dangerous, it's how they're ridden. They are made to push the limits, so they get into more accidents, just as 4wd vehicles get stuck in the mud more, because they get taken in the mud more.
There are lots of websites with tips on buying a used motorcycle (google 'buying a used motorcycle' and you'll see).
Most important for a sport bike is how well it was taken care of. Did the guy ride it revved up close to the redline all the time? Did he change the oil once in a while? And that's not always easy to tell. You have to make a judgement based on the previous owner, what kind of person he seems like to you. These bikes are often owned by young guys suffering from 'testosterone poisoning' who have delusions of being in a race all the time. A bike like this can be totally thrashed in 10k miles.
They -are- great fun. The R6 is really a wonderful piece of machinery, a marvel of engineering, all that. It's a deadly serious single-purpose machine. I would enjoy it for about 20 min. and then I'd need a chiropractor. 8^) But at 20 you could probably go longer on it than I could.
