I would want more information. You can find out the model # if you have serial #'s from the Singer web-site. I would base what I would pay on location, model #, shape of the machine/cabinet, if all parts are there etc.
You will learn to identify machines and decide what you like and don't like only by jumping in and doing it. What I enjoy most is the challenge of getting an old beat up dirty machine to work - doesn't matter what the model is.
Hope this helps.