If you are investing in SFR's, scaling can be challenging, so using the 20% of the assets' value to acquire, makes more sense than using 80 or 100%, in my opinion.

Many bears are in the camp that the credit bubble has supplied much of the appreciation we have seen over the past 10 years, and the trend is soon to break down. 

I haven't figured out how to conduct tenant walk thrus and other logistical challenges that presents itself being distantly managed.  

The live in flips and house hacking can get challenging if you and your wife are already comfortable in a nice house (especially if you have kids). 

Also, it may be a challenge to fill the park with more qualified candidates if it's in a C type of neighborhood.

Challenges?

Many investors would not be excited by your example.The answer relates to risk tolerance; supply vs demand; and other factors (location, location)...But sure, one reason why investing in Real Estate works is because renters keep on renting!

Home prices in Austin are about 75% higher than the national average and it’ll be a challenge to find good cash flow on small residences, I think. 

Challenges?

Just a huge supply of duplexes in this area.