You bring up a valid concern with Airbnb's focus on Experiences potentially pulling attention away from improving the core hosting experience.

He bought quality stocks and never sold them (never being a dramatization, as I'm sure he sold things over time when it made sense and was accompanied by a specific strategy of reinvestment).

The permitting process and the availability of reasonably buildable lots is a concern.   

My concern is that a lot of younger, inexperienced and unsophisticated folks get fooled into believing that their hard earned money is going to "buy" property in these kinds of arrangements (i.e. believing they are not "throwing money away on rent") whereas throwing their money away on rent + even more money should the option fail is a better description of what is actually happening. 

I want to help my son get off to a great start but I am also concerned what cosigning will do to my debt to ratio and I have been circling real estate investing for the last few years, ready to take a shot now.

@Adam Ramsey -Here is a map of District 24 which I believe includes more than the 4th ward, but generally outlines the area where you would need to start being concerned with the type of tenants the property would bring in, or be concerned about housing appreciation because of the surrounding area.

What are the red flags and concerns?

A low price would be important but not too low (so that it raises buyer concerns) and ideally a brand that is well known and liked by MH buyers. 

I‘m also concerned that the boyfriend and girlfriend may break up and one moves out.

I am currently marketing the office space but am concerned that the 3 residential units make it unappealing to serious potential commercial tenants.