In my neighbourhood in northern germany about 5% of the houses have them. They pay for themself in about 5-10 years.
edit: spelling
If these kinds of services don't exist in enough quantity, government subsidy could help.
They don't own the homes. They likely rent them.
> government subsidy could help.
More government money going directly over the people who most need it into the hands of the people who least need it. The property owner class redirects another crisis to their benefit.
So yes, air conditioning is very common there, even if you're poor that's one thing you will try to find a way to get.
In the ghettos it's normally an old window unit, not central AC. Also shotgun shacks, which are houses setup with a straight-through floorplan so that if you open the front and back doors the whole thing becomes kind of a wind tunnel. Not as good as AC, but better than nothing.
In those neighborhoods, you'll also often see people (especially elderly and children) hanging out at the neighborhood church or mom and pop store, where there is air conditioning, if they don't have AC or it isn't working.