Most cargo aircraft are former passenger machines that have been stripped out, fitted with a cargo liner, a roller floor and restraint equipment. The forward toilet and (if you're lucky) a galley hotcup/oven arrangement are retained in some form.
DHL certainly have nothing more than a small entrance lobby in front of the cargo net or bulkhead.
Long haul aircraft that are required to carry additional crew have some seats, usually ex pax cabin, and sometimes bunks.
For real 'crew quarters' look at some of the Russian freighters.