During the real cold Winter nights I would see homeless folks sleeping in the Terminals at EWR, they were always clean and had duffle bags so they looked like travelers.
Except I would see the same people every time the tempature at night would drop into the teens or lower, I think the PA cops had an unwritten rule to look the other way on dangerously cold nights.
It's a shame that after 9-11 you can't go into Terminal's concourses without tickets, and that lying around other parts of the Terminal with bags is not allowed under stricter security scrutiny. And like I said they never bothered anyone, they just wanted to sleep someplace warm where they didn't have to worry about getting knifed.
(before 9-11) I've seen homeless folks at EWR, PHL and DCA, probably very common (pre 9-11) at most airports near major cities.
Eastern Air lines flt # 701, EWR-MCO Boeing 757