These days it is trendy to make homes and other structures out of discarded metal shipping containers. Although not the ideal construction material they are strong, have a good deal of interior space, can be scaled (end to end, stacked, or welded "double wide" style after removing one side), and there are literally millions of the damn things lying around unused. They can be purchased for as little as $1500 to $2000 in used but undamaged condition. In recent years some architects and do-it-yourselfers have done some damn interesting things with them, building unique and often elaborate structures at minimal cost.
Recently, though, I found a great local example (which in Central Illinois means "sad") of a previous generation's version of this phenomenon: the Quonset Hut. These were prefabricated buildings built in the hundreds of thousands during World War II as an inexpensive, easy to erect (lololol), and surprisingly adequate form of shelter. They were particularly common in the Pacific, where the strategic occupation of deserted islands meant that scads of people had to be housed on desolate rocks without so much as a tree to be found. Made out of cheap materials like corrugated steel sheets and pressed board, the half dome shape provided strength, an open interior, and good ventilation when needed. It wasn't luxury living; the steel roof makes it sound an awful lot like living in half a trash can. Nonetheless it kept inhabitants out of the sun, wind, and rain. They were used as housing, barracks, prisons, mess halls, hospitals, outhouses, and for just about any other purpose that could be accommodated in 750 square feet of floor space.
At the War's end the government had more of these things than they knew what to do with, having ordered warehouses full of them in preparation with a long invasion of Japan that never happened. They were sold as surplus for next to nothing and sprung up around the country as cheap homes, bars, garages, small businesses, and storage spaces. As a testament to the durability of the very basic design, some of them are still around. Here's a neat selection of creative Quonset Hut homes and a neat art exhibition and book put together by architectural historians.