Sundance generally seems a good product. But no warranty is always at risk. If it is still hooked up and running I would probably try to find a technician willing to give it a check up first. If it is not hooked up and running I would be cautious about buying unless it could be hooked up, filled and run.
Also is the local Sundance dealer close by and one you feel comfortable with. My talk to them about what they would charge for service calls. Still a good used tub can be quite a bargain and you aren't likely to find a similar tub in that price range, assuming the technology hasn't changed that much. Probably no ozone but might be possible to add it if you want it. I think ozone helps but others are not as sure about it.