The "ghost city" thing is an outdated myth. China built up development for long term plans in anticipation of future demand, intending for them to be underpopulated in the short term.

Bloomberg - China's Ghost Cities Are Finally Stirring To Life After Years Of Empty Streets

60 minutes ran a story in 2013 using the Zhengzhou New Area as an example of a "ghost city." Today, it's population is 1.3 million.

This is one of the limitations of capitalism and that perspective, that relies solely on market signals to determine what to build when. If there's an undeveloped region, there's not going to be a lot of people want to live there. But if you build up the infrastructure, it creates demand. China still has a very large rural population and is trending towards urbanization.

Tbh, China has had a huge debt and property crisis the past few years. The US Republicans like to complain about debt (which they primarily cause, but that’s a different discussion) but China’s debt to GDP ratio is 3 times higher than the US.

Source? The only thing I could find similar to that claim was this which lists China's total public and private debt at 300% GDP. The same figure for the US is 265% GDP. Comparing only central/federal government debt, the IMF lists China's at 88% GDP and US at 120% GDP.