I want to take several long baths in somebody else's house
That feels very specific. Why would you want to take a long bath in someone else's house?
Because, I don't have a bath in my own house.
I'm so sorry about the lack of adequate bathing facilities in your home, that is not very convenient. You could end up in jail if you do that. People don't like strangers taking a bath in their house.
I'd make sure nobody found out and lock the doors.
Unless it's a friend's house or a relative's house you have asked permission for, you will get in trouble if someone sees you in someone else's house and you will end up being put to jail with a lot of fines you will pay, for something that can be resolved by you asking permission to do so in a house that is owned by someone you know. I hope you just get permission to use someone's bathroom.