Free or nearly-free land is everywhere.
In the US, go to Marquette, Kansas for a totally free lot. In Detroit, 200 bucks will get you a 4,800 square foot lot. $1000 will get you a 3485 square foot lot in West Virginia. $2000 will buy you 2.35 acres in Arizona.
Elsewhere? I doubt you would have much trouble buying huge swaths of land in much of the world — Siberia, the Congo — for pittance.
Space is not a problem. In terms of square feet, the world can fit a heck of a lot more people.
Expensive houses in big cities has nothing at all to do with over-population.
