Initially, he had a standard walled-in staircase on the second level but I found a metal guy who provided this unique open staircase concept with just a metal rail bar wall.

One of the best books to understand the concept as a whole for commercial real estate is "crushing it in apartments and commercial real estate" by Brian Murray. 

All of this is multiplied largely when it comes to housing. if you grasp the concept of the change in a gallon of milk you can grasp the change of prices where the gallon of milk will live after its bought. 

I personally despise Airbnb (the leadership/operational effectiveness, not the concept itself), but that's another forum, another day.

I feel like this is more of a philosophical question, so excuse the squishiness of my answer.In short, the problems are complexity, entropy and variability.Think back to all of the estimations you have ever given (to yourself and others) of how much effort something should/would take vs the actual.

The concept of “infinity cash on cash” is fun to think about, but once you intermingle equity like this, I find it’s more important to look at the metrics globally.  

Those strategies are great in concept.

RDPD may have had some good concepts but RK certainly didn't invent the idea of investing.

Open concept!

The book does not do the math as in the chart below, but you should learn at least the concept and BP has a great calculator that does the math close to the chart below.It looks like you asked the correct questions, but never ever trust advice from an agent or broker because nobody represents you and every broker will tell you that every property they have for sale is the perfect property for you as long as you are dumb enough to buy what they are selling.Look at thousands of properties and do the math and after a short time you will have more knowledge about the math and investing than most brokers and this no joke because I go to real estate club meeting and experienced brokers don't have a clue about what a good investment is if it bit them in the butt.