yeah like most people agree "let the buyer beware"... If i was in your position i would head back to the owners house and kindly tell them that the machine doesn't do what you had originally said it would do and ask for a refund or even a partial refund to cut your losses short.

If all else fails, you can advertise it youself in the quokka/net etc and mention that the retail price is ____ but only certain functions work on the sewing machine. Even if you can get back $150-$200 that's good enough.

I don't know if this is true or not (trying to recall of a commercial) where Janome take 2nd hand sewing machines and give you store credit. Might only apply to Janome products though... not too sure.