Condition, condition, condition, as always with 4T's or any bike/car deal it's worth going for the bike in good condition or service history. They're a great bike but spares are not getting any easier to find! However you could part it out as many guys out in the US will probably want engine & gearboxes in the future. IMO, you really need two VOR's. One to run & the other as a spares bike, just incase! If the Vor's in good nick & running right then they still are one of the nicest bikes made. I'm not biased at all.
parts have been come incredibly hard to find, especialy in the US and the ones that are still available are expensive. even here in europe VOR owners are struggling to find parts, and it's not going to get any easier. we still have on VOR rider in our group and like rob mentioned he opted to buy 2 other bikes just for parts so he could keep one bike active.
be very mindfull of what you're getting into when you're thinking about buying that bike.