Anything To Look For When Buying A Used Dehumidifier (Don't Want To Get Scammed)?

I'm in the market for a dehumidifier and and
have seen some good deals on Craigslist. I'm
looking for a Santa Fe, Phoenix, Dri-Eaz, type
of commercial unit.

I'm worried about getting ripped off by buying a
worthless broken piece of shit for $600-$900.
Is there anything a should check for when I buy
one and are used ones usually pretty reliable? I
can't think of any quick and easy way to test one
out before taking it home.

Thanks,

treetopmmmp