I’d bet that today there would be permitting and insurance requirements to run a boardinghouse that no one in the 19th century could have imagined.
In my impecunious younger days, I had to live with quite a variety of roommates at different times. I expect to see a lot more residence-sharing and informal cooperative situations happening in the coming years.
DW and I are retired and own a few 3 BR apartments as an inflation hedge/small business/retirement gig. We started seeing roommate situations show up 2 or 3 years ago and the trend has continued and even gotten stronger. About half of our units are rented to people in situations other than the traditional family.
I am not saying it is good bad or indifferent, just that is what is happening.
And, we are in Oregon, which has statewide rent control. Just like economic theory would tell you this has caused a huge shortage of rentals. Fortunately, the rent control is fairly toothless so far, and prices have gone up pretty rapidly also.
BUT, there is no situation that a RAT politician can not make worse and I am anticipating much more stringent rent control in the future.