Depends on what you are willing to pay I guess, you could get one for £800, you could also pay £1500 for one (I wouldn't go more, personally). JodT5 has put a guide up here:
http://www.volvoforums.org.uk/showthread.php?t=46939
Have a read through that, it'll highlight some key points to look out for when you are looking at a car.