This is a brilliant way to add square footage. A minimal, lightweight, inexpensive roof and deck give you an expanded living area (during good weather). The warmer the climate, the better this works. You can barbecue, eat, and socialize out on the deck.
I saw a place in Baja where the gringo owner, who came there only periodically, had built a small concrete block unit with a steel door where he locked up and stored all his stuff. He had a large roofed-over with a split bamboo covering for shade; when he came down to his land, he opened up the unit, pulled everything out (including hammocks), and lived mostly outside.