I think it depends on what kind. I wouldn't buy a used singer made with plastic parts, but my mother's singer from the 1950's is a work horse. I have a Janome that is 20 yrs. old. I'm using it for almost all my sewing. It only has one "bell" and no "whistles"--a computerized buttonhole. I think about a newer machine, but I also think about paying other bills! I think you can get a reasonbly priced used machine if you look on Craigs list or at a local shop, and try it out first.
good luck!