Seattle's flop houses are mostly gone now...Spokane's are disappearing rapidly and is creating a new homeless problem in an area that used to be fairly immune to it (because of access to cheap housing).
China/Hong Kong and some of Asia have created a new spin on SROs with capsule and pod housing, China leverages a lot of sub-basements for SRO housing (without access to windows because underground), while Japan has cheap 2.5 tatami sized small room apartments. None of these would be allowed in the west, they are barely living, but maybe we should start thinking about them as an alternative to a much worse situation?