Try to turn it by hand instead of kicking it. That's what I'd do if it hasn't been run in that long.
Look for rust in the tank. That'd be the biggest thing other than a seized engine to me. It's fixable, but it's a bitch. If it's rusty, you should get them to knock the price down. Explain to them that it's like a $40 to $60 kit to strip and coat the tank, plus hours of your time.
Obviously if things like the magneto are rusty, think twice about getting it.