Look for an original model made by Hobie. I believe they were made until the around 1990 or so.
I've heard mixed reviews on the quality of the Razor-made models; seems like construction quality is nowhere as consistent.
I had a 1985 Hobie Power Skiff and never had an issue with it (bought it when it was over 25 years old). Read through some of these pages and you'll find a lot of good information on common issues and remedies for pre-owned boats; it was enough to convince me to get an older boat over a brand new one.
Keep an eye on Craigslist, set up alerts, have cash in hand, and be willing to drive a little bit to find a deal. With the amount you save over a brand new model you can likely repower and have cash leftover for fuel or to do a little customization.