As someone not from America, this seems insane to me. Who's stopping you from renting not living with people you aren't related to and why the hell are they all

As someone not from America, this seems insane to me. Who's stopping you from renting not living with people you aren't related to and why the hell are they allowed to tell you what to do with your own bedrooms? Equally, is 6 bedrooms normal? Sounds like a lot of cleaning.