Since lamp hours can be reset, you really have no way to know, just how many hours will be on the lamp currently in the pj. So in the price, consider you'll have to buy a new bulb for it. If you don't need one after viewing it in action, then you've put off the time you'll need to buy one.
If you can't view it working, you may be getting a unit with bad convergence, and with no free support from epson. Something to consider. You also won't know if it was used in a smoke free environment or might have dust blobs that haven't been corrected. Alot of possible problems on buying a used unit, you can't actually see working.