I think modular/pre-built/kit homes can be a really great option, for a lot of reasons, but they probably won’t do much for home affordability. The restricting factor is land. There are only so many detached, single family homes that can fit on any given area of land, and the land is getting full. At least, it’s pretty full in the areas people want to live. You can get a pretty cheap house already if you’re willing to live in less desirable areas.