I'm considering purchasing an investment property - 4 bedrooms, 2 baths, but the catch is that the 2 baths are on the 1st floor and basement, and the second story has all of the bedrooms. In order to resell this house, I feel like there needs to be a bathroom on the second floor. Any idea on cost to add a bath from scratch (I'm in a Boston suburb) and things to look out for/be aware of? I'm going to have to carve out space from the bedrooms, but do I need to make sure there's a window? Does it have to be directly above plumbing on the first floor? What are some of the things you would look for if it was you?

Thanks in advance.