This is a 680T, isn't it? No picture window?
Does it have bleed air pressurization or hydraulic? I'm guessing the latter, since I think that was part of the Century upgrade, in which case Glenn can tell us all about that system.
Also interesting that, while the last annual was in January 2019 (according to the ad), flightaware shows flights up until October 2020. That's both good and bad... bad if it was flown illegally, but good that it was flying at all.
I think the purchase price is just a down payment on this airplane... can you still do the Century conversion?