there are many things you can do, but essentially you want to make it profitable for builders to make houses at a lower price point, or give the average person more money. Some approaches (not all of which I'm endorsing):

- reduce restrictions around planning / construction / etc (because it takes time and expertise to comply, both of which cost money)

- find a way to bring in cheaper labor, or make it possible for construction companies to hire the same labor at a lower price. Maybe a subsidy, maybe reduced taxes, maybe relaxed labor laws

- add a subsidy for homes

- make your citizens more wealthy, so the price is no longer above their means

- outsource construction to a place that can build it more cheaply (eg, prefab homes)

> - find a way to bring in cheaper labor, or make it possible for construction companies to hire the same labor at a lower price. Maybe a subsidy, maybe reduced taxes, maybe relaxed labor laws

It's far easier than that: just have your regional/local government finance urban renewal projects that increase occupation density. You can even tie the project to the expansion of a public transportation system.