This is one of my all-time pet peeves, ranking right up there with reporters who say:
"the military pay no taxes"
"Food at the Commissary is free"
To set the record straight. Military housing is not free. Service members receive a housing allowance as a part of their overall compensation package. When a service member lives in government quarters, they forfeit this housing allowance - this is, in effect, their "rent". Not free.