The third world isn't a good target; there's no permanent dwelling shortage. The reason why you often see people homeless or living in squalor in the third wor

The third world isn't a good target; there's no permanent dwelling shortage. The reason why you often see people homeless or living in squalor in the third world is because they were uprooted by war, famine, or natural disaster. They often need short notice temporary dwellings, rather than new permanent ones as this would produce. So there's a market for "popup housing" in some of those countries (and even in the US for natural disasters such as Hurricane Katrina), and the Red Cross and similar international aid charities make some use of those. Erecting concrete structures that would be hard to disassemble is likely a non-starter (in particular as it requires a plentiful supply of water which may be unavailable in an evacuation zone).