I'm an engineer not a mathematician so this may not be the most technical of descriptions, but should convey the general idea....in layman's term: the mortgage payment is mathematically determined based on your interest payment being logarithmic (i.e. it reduces each month) and your principal payment being exponential (it increases each month) such that the total payment stays the same. 

Mathematically I doubt there is anything that comes remotely close to 2nd place as "unrealized". 

If you're looking at large exchange-traded companies the market does a pretty good job of pricing assets and data can yield volatility, variance, etc. figures that would aid in establishing mathematical defintions of risk for a given asset.

Keep in mind the author of the hook on this that is touted on this site is a real estate professional and a Broker with an extensive network its all good in theory .. but implementing it on those size assets is a whole different ball game.its why turn key is popular u may save a bit on do it yourself or get the refi.. but finding the deal that works mathematically to get all your money back is a very big challenge in most markets given the competition.. 

If you want to learn about technology I️ would Learn hard skills like coding or Mathematics.

It is a mathematical certainty that socialism will double the price of Seattle real estate.

The issue is not whether it's mathematically correct, but rather whether it is appropriate.

But a scientific theory cannot ever be proven true for all real world conditions.Only mathematical theorems can be proven (in fact, the formal process of doing this is called a "proof").It can be shown mathematically that under specific conditions that if the increase in the price of any limited good outpaces inflation long-term, it will become unafforable.  

Compare this to heuristic, a similar concept used in mathematical discourse, psychology and computer science, particularly in algorithm design.There are so many MORE expenses and benefits to a rental property that are not even covered in the 50% "rule of thumb."

Mathematically they could do 10+ projects but we settled on 8.