If you buy from an auction, make sure it comes with the original box. That can save much heartache in preventing damage. UPS and fedex are not careful with the boxes no matter how many times fragile is written on it. I have bought from auctions several times and all good outcomes except 1 where it was not boxed properly. It was totaled, but the seller refunded me and dealt with the shipping insurance.
I have bought a gently used bernina 770qe from a dealer that had used the machines in a class. I love that machine.