I don't know anything about the 17' but did have a 16' years ago. One thing I do remember about buying used was to check the posts or pylons that come up out of the hulls that the trampoline frame attaches to. On older boats they tended to become loose and would leak. Other than that check the condition of sails, the tramp, the underside of the hulls for wear if the boat is dragged up the beach a lot, and all the usual stuff. In addition check the rudder gudgeons as those also may be loose on a used boat. Like any boat if it looks good it probably is and you don't have to worry about engine condition. If the battens in the jib are already hinged that is a bonus. There used to be all kinds of aftermarket things to make a Hobie better, some may have been incorporated into newer models but again I don't know. I owned mine a long time ago. I sold the Hobie and got an 18' G-cat and all in all it is a much better and more refined boat. That said there was something raw about the Hobie that was exciting.
Lots of fun with one of those for not a lot of money.