I suppose it would depend on the country and how you define 'house' but even then I think you're being overly optimistic with your timeframe options. I don't have a clue how much the cheapest house would cost in the poorest country or some isolated rural location in developed countries but I think it should be reasonably safe to assume it can't be less than $5,000(?). And I'm not sure if we can reach $5,000 by 2020. Maybe more like 5 - 20 years if I were to guess.