I think the inner dimensions are about 3m * 3m.

Aha, a hermit hut in the woods sounds perfect! In Finland many families have their modern homes, and then a summer cabin somewhere in the countryside. Those summer cabins used to be very low-tech, often without electricity. But as the post-war generation has been growing older and wealthier, they have equipped their cabins with all the modern conveniences so that they become like second homes. (Actually, I know a few families who mostly live on their cabin, and only sometimes visit their city apartment).

Hehe, but a simple non-electricity cabin would be a nice project to build! (Sometimes I dream that if I'd magically become rich, I'd buy a piece of land next to the lake. And build a sauna and small cabin there.)