Here’s my current calculus in my area of New Jersey NJ - each 1 furnished room rents for $1000-1200/mo with like 5% vacancy and each furnished 2 bedroom apartment rents for $2500-3000/mo with 10-15% vacancy.

It becomes a calculus exercise. the extra thousand raises seller costs, but should cover the extra costs at the margin in most instances. 

My mental calculus is that I want returns in excess of 25% above what the passive S&P 500 Index has returned historically (~8%).  

This reminds us of a 2nd grade math teacher taking all the credit for his student getting an A in calculus.

As a lender, I'm sure you know a million agents, but you may consider finding one who owns investments, and therefore understands not only the mathematical calculus of divesting from an investment, but the emotional ramifications as well. 

Gotcha...The calculus of that decision is different if you are investing from overseas.

However, I don't do it on mine because its very questionable to me whether the total cost to total benefit calculus really makes it worth while for individual SFR properties that are not cookie cutter duplicates of one another, equipped very differently, bought at different times, in different locations, etc.

I would say the majority of people who try to invest when they do not have a degree in a Financial field will do two things.... 1) look at the book and get very sleepy and 2) Tell themselves that they don't need these "complicated" calculations.The reality is that when you speak with the highly trained Pros, they ONLY speak about the IRR and other derivatives of it.It doesn't matter what you invest, the professionals who Invest need to know it.In some cases, heavy calculus is used for trading, such as in the Quant professions.This book gives you all the math you need which probably goes only the the extent of intermediate school.... say, 7th Grade, but many adults are very intimidated.

To be honest I feel like a 2 year old would probably feel in honors calculus!

I’m going through the calculus right now on whether to keep or sell my first investment property.