For that price I certainly would buy it. It wouldn't cost all that much to have it humming along. Featherweights are so popular that the prices are still quite high especially for a so called mint condition one. Course there are the few lucky people that have found them for virtually nothing but for most of us don't find those.
Basically it just depends on your available funds and the ability to have it tuned up, electrical cords checked, etc. But if you've wanted one forever, then I'd go for it. Quite possibly the needle isn't placed in the machine properly and their may be minor issues that are easily fixed. Finding the belt isn't a problem at all. The are easily available. Did you try to post this to Billy our expert on vintage machines? Any concerns you have would be addressed honestly and accurately by him. Plus all the other people on the board that have them and have faced the same issues you are concerned about. Post on the Vintage Sewing topic area and you'd be amazed at the help you'd find there.