That statistic regarding available housing ignores a lot of things. Where do the resources come from to keep this available housing in livable conditions? What is considered the minimum livable condition for these spaces? Who is responsible for keeping these spaces livable? What guarantee is there that any of this available housing is within reasonable travel distance of other necessities (not even speaking of employment, there’s urban food deserts to consider)?
At some point there is a required expenditure of resources, even if enough physical homes exist.