Ask every question you can think of. I bought a Bernina pd $2,400. Pd to have it professionally packaged. 2 boxes came - both absolutely wreeked of cig smoke. Machine right side behind fly wheel was yellowed, repair slip that came to show it had been cleaned and in good condition had a whole different seriel no. than was the machine, the packing material included JoAnns bags and cardboard (literally with that name on it - imagine UPS going to JoAnns for their packaging!). This machine stunk so bad even my kids complained when siitting on the kitchen table. I filed complaint w/Paypal. Seller personally phoned me ranting - her position "buyers remorse". And I thought I had done my homework - good seller with positive selling record. Evetually I got my $ back, less $110 shipping fee, but it took 40 days and tons of time, work and emotions.
My recommendation: Only pay out as much money as you are willing to throw away. I understand I was one of the lucky ones.