Building houses is probably generally allowed, but not an easy solution.

Someone who migrates to another country, to work there in a regular job, can get a regular apartment. But everyone wants to live where the living conditions are best. You can’t build infinite housing in those locations, and the increased demand drives prices.

Someone who seeks asylum is in an entirely different situation, and housing them is a different challenge. Building a house in a nice place costs 10x what it costs in a remote country region. But now people have nobody to integrate with and less social options.

Any house being built costs money. Building houses for people who are still in search of employment is a bad investment. Nobody wants to build those houses. They want to build the nice houses in the nice places that will gather lots of rent. If you want to have the houses anyway, because maybe the people are already here, you probably have to use taxes for it. Some citizens will never be able to accept that, creating conflict.