I have picked up a couple of these at garage sales. They are nice machines. I have a friend whose hobby is cleaniing and refurbishing the 6000 series of Vikings. The only negative I can think of is that the dials can freeze up with age when not used. That is something that can be fixed, but if you have one of those machines, you will want to use it regularly to prevent that problem. I think my friend usually gets about $250 for one that he has worked on. I am sure you can get them for less if they haven't been serviced but are working ok.
Dayle