I purchased my machine from a dealer, a shop near me. Some one had purchased t it and returned it with less than 10 hours of use. I got it for less than half of its original price because the model was about to be discontinued in the next few months. I have had absolutely no problems with the machine. The dealer was a certified Pfaff dealer he and his repairman did repairs on all models, old and new. The shop closed but the repairman went to another new shop that opened in the same town.
I would not be the least bit hesitant to purchase a used machine from a dealer. They want to keep you as a happy customer.