I've worked on a few of these types and they're good little machines if working properly. The outside being in good shape is a plus, but who knows what the history of the machine is... If they're not sewing correctly they can take quite a bit of work to get going properly. If you can try it out before you buy, that would be ideal. But, if you can't at least make sure all the controls move easily and correctly. They can harden up inside with lack of service and use. I can't tell you what you should pay. That's up to you to decide, especially if it needs servicing.