Is this just a rule of thumb, or is there an explanation (in a micro- or macroeconomic sense) for this calculation?

It is best to calculate out your holding costs associated with the time that it would take to get the squatter out. 

Hello:I am not sure what interest rate to use while calculating cash flow.

 I’m starting out and I’d like to know how would you go about doing an inspection on a potential deal to calculate rehab costs if the property doesn’t have any services turned on?

Any advise on any of these numbers or whether I am calculating this properly.

Then later find out in underwriting that the loan officer did not calculate income correctly or used rents that do not qualify.You want to ask to see the math to see how are they running the approval it’s not just income, and rents it’s also what are the annual taxes and annual home owners insurance they are using to qualify.

Look at an amortization calculator. 

The single bedroom apartments must be about 1488 square feet from my calculations because 35,719 square feet divided by 24 is 1488 which is quite large for a single bedroom apartment..  

Why are you calculating the monthly rent from the ADU if you will live in it for your own use? 

I posted this on another thread but I'm honestly getting better returns (IRR and CoC) on a HYSA than Indy Class C house #2 projected out 15 years on my calculations.