Anyway, just my observations. 

Go to open houses and observe the list I laid out above.

You might have an easier time finding a good to great deal on a duplex but again this is just my observation. 

I'm comparing the boring period from 1996 to roughly 2004 with the period roughly 2010 to present, observing based strictly on the charts that the boring period is a positive slope and the 2010 to present period is a flat slope, indicating to me that we have not " ... made it back to the trend line that was established early in the chart."  

but I would very much agree with Jeffrey Butler s observations!

In my observation, they are often past the peak of their useful life span.  

I'm about 30 years too late getting to @Bill Gulley free course, but my observation is that there are many variations of ways to help kids (or grown ups) learn the power of real estate and everything associated with acquisition, building, owning, managing, etc.  

They are only my initial observations so far.  

So the drill would be 1. enter assumptions such as rent/expense increase and vacancy, 2. observe the impact on the dependent metrics.- I would also reformat the income/expense worksheet to the standard rental property format which makes it easier to analyze.

My general observations are that (1) you seem like a very thoughtful and diligent landlord and (2) you need new tenants.