Grand Rapids is a very small metro, but its housing market is as hot as Denver or Portland. As a city in Michigan, this is highly unusual. I suspect there is something special about it. Is Grand Rapids limiting development? Does it have a strict zoning or somehow a successful city planning?
Its economy is fine but nothing special. There are abundant of buildable flat land around it.
A housing shortage in a Michigan city, there's got to be something I do not know.