Most important: Make sure they have a clear title to the skis, and trailer if you are getting that as well. If they are still under lein that complicates the deal significantly.
Take a flashlight pull the seats and look inside for signs of rust or corrosion (white color on metal) which may mean inadaquate flushing after salt water use. I always ask about the number of hours in salt water. Use the flashlight to look in at the impeller from both sides. There should nearly be a flush fit to the sides, and no dents etc.. If you can't do a test ride, I definitely have them hook it to a hose and run the motor for 5-10 minutes. Rev the throttle listen for problems. Look for excessive smoke that could indicate burning oil. Pull the air vent cover (2 screws and some clips around the edges) and look at the air filter (should be clean and dry) not oily. Look at the battery connections. Look for standing water in the bottom of the ski. Ask to see if they have a receipt for the 10 hour service, or some documentation if they did it themselves.
Sounds like you are getting a great deal. I'd jump on it if everything checks out. I don't think there is any savings in maintaince with this model ski compared to the newer models. The service schedules look the same, and spark plugs, oil filters, etc. will all be nearly the same price. You may get slightly better gas milage on the newer FX models (not the SHO), but certainly not enough to even consider this a negative.
