How do you fit a half bath in a narrow row house?

[Mauricio Botero]

Hello BP,

I have been looking at investing in North Philadelphia (Fishtown, Port Richmond, etc) and one thing I quickly learned is that most of these older row houses do not have a half bath on the first floor. I also see that a majority of these houses fit in two categories:  

a)the stairs to the second floor are against one of the long walls near the front door

or b) the stairs stick out from the wall perpendicular separating the living room space from the rest of the house (kitchen, dining room). These homes and lot are usually within 14 to 15 ft wide and 50 to 60 ft long. 

Did not find much on BP about the subject, so figured I'd start a discussion on it. Where and how would you add the half bath in the first floor in these style homes? 

- What if this was a complete gut and you could have a clean slate, where would you add it? 

- What if this is a small remodel and you are trying to keep costs down, while still getting that half bath in?

- What other variables or specifics would you need to be able to give a good answer?

Here are one of the examples I've found that I like the most if the layout of the house allows for it:

[Bart H.]

Is there room under the stairs?  In the past I have seen some older homes where the toilet is set to the low side of the stairs and the sink to the back near the high side of the stairs with a door to the half bath coming out perpendicular to the stairs.