In the end it depends whether you think it is a good deal in the end. Would also recommend looking around at some scooters as well. What year is the bike, how many kms are on it, is it driven year round or just in the summer months, how often he/she has the oil changed, what other repairs have had to be done on it, what problems he/she has had with the bike, how easy does it start, does it idle well or is it always dying, is it spitting out lots of exhaust when you drive it. Obviously you want to test drive it, see how it runs, does it have enough power for your needs etc....
In the end, the choice is yours, always try to bargain. I bought a bike that was 2 years old with low miles that was a 125cc for only 500,000....
