Just tell them to go live in a van down by the River Rouge, Mr. Farley.
However, to someone for whom rent is an onerous expense, vans and box trucks are prohibitively expensive, especially when you consider 10 year TCO.
Pretty much everything that makes housing/living unaffordable is a result of intentional regulatory decisions between about 1960 and 2000 (with the biggest exception I can think of being the coopting of the IBC by various product manufactures, that picked up in the 2010s and beyond).
You can't live in a van or other mobile thing because zoning. You can't build a non-mobile thing by the river because wetlands. And even if you could the thing you want to build can't be build because the rules and the codes are riddled with carve outs to make work for well lobbied industries.