And flint is not the only city like this with shrinking population yet rising housing values. A quick google shows me also Rockford, IL, Decatur, IL. Youngstown OH. Saginaw, MI. Binghamton, NY with no apparent end to the list
While it's true that zoning worsens the problem, cities with essentially no zoning rules also have have rising housing prices.
The crux of this universal problem is that housing has been turned into an international investment class rather than being housing.
That and that retirement support is so dismal, individuals must have large returns on home purchase to avoid life threatening poverty in old age.
So of course change zoning rules, it's bound to help some but it's not the core problem.
[1] for the curious, start here https://en.wikipedia.org/wiki/List_of_shrinking_cities_in_th...