I also am playing around with the idea of making a 3rd bedroom in one or all of them if possible as they have a lot of wasted space . 

He said the old iron pipe had deteriorated and he would have to cut in to the wall to replace the drain pipe.

I know I have a lot more to learn but I don't want to waste time and feel I should take action pretty soon.I started building credit already and I read/listen to real estate related stuff everyday.

Write it on the walls, tattoo it to their arms if you need to. 

On a few of the interior walls there were red x’s drawn in what looked like red marker.

I feel like I’ve hit a wall.

@Jaron Walling The meters aren't split so I'm responsible.

Like @Jaron Walling says.  

Basement has basically a hole in the wall in just that section.

Is there a rough way of determining the number of apartment units that can fit in a building while accounting for space loss due to walls, hallways and staircases?