"Regression to the mean" is the mathematical term.Fix and flipping, OTOH, is a job.

@Bill Bonds found a website that shows more of the mathematical way of answering your questions.

The result is a file that acts as a mathematical sand-table, where you can present data in any way you wish - any way folks should check it out - gotta go, takings the kids ice skating.

It was not a mathematical cost calculation like footings, framing, roofing, etc. 

I made a big mathematical error I just corrected.I ran the numbers using 30 years of S&P 500 data. 

Hey,a very interesting historical analysis and model of rents in San Francisco (with data source on GitHub).For numerical guys such as @Brian Burke, @J. Martin, @Minh Le etc etcSome excerpts:"Overall [rents], they wen...

Einstein also believed that the formula for compounding interest was the greatest mathematical discovery of all time. 

Let's try a mathematical simulation to see if @Scott Trench is wrong.Lets say you have $20,000 and buy a $100,000 rental property using banks money.

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".