We have a 7x7
Rubbermaid Roughneck shed at our seasonal site. We have the one pictured on the home page. Our Destination Trailer has no outside storage, except under the bed. That storage is large, but only accessible by a small door.
It's not the most portable; the box it comes in will fill a standard bed of a pickup, but it can be put together in a couple hours (I put mine together by myself) and taken down even quicker. We have ours on a platform, but as long as the ground is flat and level it will work on bare ground. Doesn't require anything more than normal hand tools. Rubbermaid does make smaller versions that would be more portable and still be large enough for a freezer.
-Michael