here are some things to look out for when buying used projectors,
remember about what the rated lamp life is , this can vary from 2000-20000 hrs , you may buy something with 1999 hrs thinking you will get lots of use out of it, but you won't.
also take the lamp hours with caution, this is easy to reset so if it looks too good to be true :) it proberbly is!!!!!!!
if there are more than one picture look at things like the condition of the body, if it has lots of major scuffs and scratches this unit has not been looked after and may have bigger problems in the long term, also make sure the lens is not scratched as sometimes this can affect the image quality,
if it has a projector usage counter check what the hours say, if it is a very high number this is bad news as the unit is on the way out and could have major problems in the feautre :(
and remember if the deal looks to good to be true unless there is some way to prove the unit is worth the money you are paying, walk away you could be stuck with a unit that has major problems in the feature and many end up in the skip.
follow these things and you could have a very decent projector
one last thing, if you are buying a LCD projector when you get it clean the filter(s) before use as sometimes people don;t look at them or even know they need cleaning