i always like to bring a friend along just to ask the questions that the seller might lie about. see if he changes his story at all. i know what to look for when buying a bike , but having another set of eyes and ears never hurts.

if you dont have faith in yourself then wait for a friend.. but not every mechanic is knowledgable and not every teacher has all the answers.

 

Look for fluid leaks too. Oil and coolant. Start the bike and let it idle for a bit and get to operating temp (a test ride is perfect, but if you cant ride it, let it idle for a bit). This will circulate the fluids out any leaks and hopefully be visible. Plan to stay and ask more questions after you turn the bike off to give some time for any fluid to drip to the ground. Peer around inside the fairings with a flashlight if you need to looking for fluid or anything else that's "not right" after warm up. Good luck. And one more thing...an honest seller will usually sit back and not pressure you. If he's acting funny or something about the guy is weird...say thanks and find another bike (there's plenty out there).

 

Two differing viewpoints - mine is more cautious, because I've done what you want to do, and got burned doing it.
Steve's advice is sound, too, so if you feel you have enough ability to tell a rattle from a knock, a worn camchain from a stuffed bearing, go for it by all means....!
All the other guys have given sound advice, too..........
At the end of the day, you and you alone have to live with the decision you make - we can only advise what WE would do.
Pity we can't put old heads on young shoulders..........[X(]