If you have a piece of farm land then, with the right permissions, you can build a shed on it. Well, it's only a shed, 20sqm maximum in size, but, when no one is looking, you can make it quite comfy. There are more than a few of them down in the Mojácar riverbed, fitted out with bunks, a chimney and an oven. They are used for weekend parties or other entertainments, and at a pinch, you can add a fence, an ornate gate, a roofed terrace and goodness knows what else. Water and maybe solar. In other words, hopeless and edging on the Spanish art of the impossible.
So, an artfully worded advert I found today, for a piece of land in the boonies:
'Plot of land in Mojacar village/Turre, with 6.300m2, you Can build a small casita of 20m, or ideal for a mobile home, camping car, beautiful views of the valley and fruit trees, electricity and water on the edge of the land, Good access road, 5 minutes to the beach...' The price is 70,000 euros by the way.