If you look hard and long enough you CAN find boats that people have taken care of and done the maintenance on. You can tell that this boat has NOT been loved. At least not in the last 10 years. I would really stay away from it. Looks like a huge project boat. Any used boat purchase is a gamble, but at least improve your odds. Spend more up front to save time, hassle, and money later.
Here is a boat looks like it has been loved:
1987 SN 360hrs $9500 with a cover and stored under a roof:
http://adcache.boattraderonline.com/6/0/5/87117905.htm The 1989's are better, IF they have been loved, because they used a better type of fiberglass from that year on. Here are 2 in Florida that look to have been loved:
http://adcache.boattraderonline.com/6/8/7/10312487.htm http://adcache.boattraderonline.com/6/0/3/88107003.htm I understand if you don't want to go into much debt. That is smart. But if you are in a position to spend a little more, you can get so much more boat for $18-$20k. The Sport Nautique's have the same bottom hull as the modern SAN's so they will make the same wake if weighted properly. Plus you get an open bow, fuel injection (big), more horsepower, and a newer more reliable boat. And no wooden stringers to rot.
Here are 2 worth a look:
http://adcache.boattraderonline.com/6/8/6/87999886.htm (make sure it doesn't have engine rust from salt/brackish water around Vero Beach)
http://adcache.boattraderonline.com/6/5/4/86830154.htm This one looks the best, but is also more money. But you get a tower (worth at least $1000 right there), and a well maintained, one-owner boat that has been stored out of the water, under a roof and with a cover. But find out if that price includes a trailer.
Good luck. Older Nautiques are very well built and reliable and have a great wake. Just pick a good one, not just the cheapest. Save up if you have to. And always talk them down on price. Let us know what you end up getting.