I love buying "broken" machines. I used to work at a retail sewing machine dealer and after I sold a customer a new machine; she gave me her Necchi 535 and said it didn't work very well. Turned out she was using the wrong bobbin,there was about 1/2 a spool of thread wrapped around the inside of the hand wheel.
Heaven only knows when it had been cleaned or oiled. Once I fixed all those issues, it sewed like new. One of my daughter's friends got a good machine for free. He trashed his plastic wonder that was bad news from day one.
Sharon