Those places are very shoddily built and have structural problems and cracks within a couple years of being built.
Wait until the SF-Oakland bay bridge starts cracking. It already has.
Anyone remember the Chinese drywall problem in the south from about 15 years ago? The crappy imported drywall was out gassing causing copper wire, pipes and HVAC components to corrode and fail. People were made sick by it. Where it was found the entire house had to be completely gutted, refinished and rewired. Every material in these ghost cities are questionable at best.
Check this out: