Used Computrainer?

So what is a nintendo based computrainer worth? I really know nothing about these, so what should I look for in a used one, what questions should I ask?

Are the Nintendo ones even worth looking at? Or just buy a regular trainer till I can save up for a new computrainer?

Thanks

Buy a Kurt Kinetic or a 1-Up.

Get the newer model!! I still would love to get a velotron, but have had not luck finding a used on yet.

Dave