I like e-bay but when buying second hand there are things to remember.
There could be fret wear, uneven frets, lifted bridge or bellying of sound board (on acoustic) twisted or bowed neck, is truss rod working?
It might need more than a regular set up. If it's nearby and you can try it/check it out then that's fine. Of course it may be so cheap that you can afford to take a chance! Steve