There are 2b+ people living in "inadequate housing", don't have sewers, don't have running water right now, we can't even fix the problem now, we're not going to fix it better when 2b more need AC to survive every summer
https://unhabitat.org/news/13-jul-2023/the-world-is-failing-...
It's not just expensive. Steel and concrete are some of the largest drivers of CO2 emissions and toxic waste, in the ballpark of 15%! So really the only sane choice is to avoid building new homes whenever possible and try to keep old houses in use as long as possible.
Sure, we could bulldoze everything and build new stuff that can handle a +2C, +3C, +4C, etc... world, but that's expensive.