Since you have stable income there's no reason to shoot yourself in the foot chasing an investment property. 

The international property maintenance code which is the document many building department use for determining overcrowding complaints is based on the followingMinimum 70 square foot bedroom 1 occupant Minimum 50 square feet per person for two or more i.e. minimum 100 square feetIt does not address ages or relationships Many zoning ordinances have rules of more than 2 or 3 persons unrelated by blood is a violation.  

Unfortunately, their demo already included the garage doors, 6 windows, a half bathroom, staircase, the exterior siding, all the wall and ceiling insulation, and they poured new footings and framed in the garage opening.

Unless you have an extensive knowledge of what you are looking at you are likely to shoot your self in the foot. 

It pays for our mortgage plus a little extra, and it's a 350 square foot room with no kitchen and no laundry facilities.

We could extend and file after but I don't want to start off on the wrong foot. 

Just do the math for your area per square foot for similar materials.

It's nice to have a foot in both worlds.What major will help you in real estate? 

We own a house.  1600 Sq Foot FULL of stuff. 

I'm hoping this will be my foot in the door.