She is a single mother with an adult daughter that has just graduated high school and i think will be going to community college.  

They successfully did that in DC and got approval to do it in a residential neighborhood for a house that now rents to college students blocks from campus.

You would need everything needed to become a landlord: help from an attorney, rent permit from the city.

I remember seeing the Chinese real estate market booming when I was attending college and working in Shanghai in early 2000.

But, it depends on the city. if you applied for permit already (of course, you're changing panels), you need to ask the inspector, they are going to catch it anyway.

Single-, multi-, I don't care, I'm just looking for cash to help get the kids through college.  

The variables I think I need to consider are:1) use of metal vs flex duct2) type of unit installed and warranty3) will permits be pulled / work done by licensed professionalI want to save money but don't want to create headaches.

If I would have started earlier, I could have marked a property as a potential sale once my kids get to college age, but at this point I am ensuring my retirement first then college education second.  

My first two projects are in College Station and Conroe. 

My first rental experiences are with college students, which has been exceedingly easy, and I'd like that trend to continue.