While we tend to look at averages and global totals, the reality is the population decline is going to be very lumpy. After we reach peak global population, Africa will still grow for a while. Even though Japan peaked ages ago and there are empty houses everywhere, Tokyo is still growing and houses are being built.
When capitalism starts to falter (low or no growth due to fewer consumers and workers), it will affect some places quicker than others. And then people leave for somewhere more prosperous, even another city in the same state, exaggerating the effect in both places.
We have seen this recently, in a way, in San Francisco. While the cause was the pandemic, and partly because people could now work remotely, it does show how much mobility there is in where people choose to reside.
US Census data shows that the median household income in the area containing San Francisco, Oakland and Berkeley fell from $121,551 in 2019 to $116,005 in 2021 – a drop of over 4% in two years. New York City saw a similar decline.