On one lease in near Aberdeen we had an old tree planters hut which we fitted out with a woodburner a gas cook from a caravan and eventually 12V lights..
On other leases we've bought "scrapper" caravans and fixed them up until they were water tight...
One of the caravans was eventually smashed up by vandals but that was after we'd come off the lease and it was being used by somebody else.
We would arrive at these leases at some ungodly hour in the morning after driving up from "Englandshire" as the locals put it, and it was always a relief to see the caravan /cabin still intact.
A proper static caravan is much better, but you then have the hassle of transporting it and once its on the ground, its essentially stuck in one place so alot thought has to go in its placement.