the problem with 2nd hand as i see it, is all but inviable. It is the wear on the springs. Some people just about tiptoe around then deside its not 4 them and sell. Others really hammer their kit , bottoming out left right and centre ( i know 1 or 2 who have gone x2 up in the weight range 4 this reason).
I know which 1 id prefer to buy but how to know?