> Renting a private room was possible on nearly any wage 50 years ago

I think others pointed this out but I don't think you can find any data to prove this because its not true.

I'm not a historian but I have seen a number of old movies and in those movies it was very common for the characters to be some poor schlub with a full time job at the factory living in some sort of group home/flophouse situation. Movies tend to reflect stories that resonate with the public at the time so I suspect that is because this was a common situation. I'd much prefer a single roommate in an apartment to a flophouse.

50 years ago was 1976. I would be surprised if large numbers of adults in 1976 in the US were living in the same room as other adults, unless they were romantically involved.