What people don't realize:Stockton appreciation ranges from 6-9% historically, median is 7%Austin TX median is 5%.If one moves asset from CA to TX, mathematically you will lose money.

I'm talking about the science of money.It's a great combination of psychology (individual and group) and mathematics.

All the answers above make mathematical sense FOR THE BUYER, but do not neglect yourself.You need to make a fair wage too. 

Anyone that tells you to do these things are not giving you an answer based on mathematics, data, or fact.

Because it is not my own experience, I cannot say anything else on this.)My decision was ruled purely by two mathematical considerations:1 - Not being a bettor on market appreciation, I invest for cash flow.

Ok so two things here: First, I want to comment on the general principle of using home equity to invest (HELOC OR cash out refi):There's nothing wrong with this at a theoretical level, and if you think you have a high probability of earning a greater return with the cash invested in a rental property than in your home equity, then it makes mathematical sense. 

If you can invest the extra money at a higher rate mathematically you will do better.

What the rule gives you is a quick high level analysis of a property.There is mathematical logic behind 1%.

Do you use a mathematical approach (using ROI) or more gut instinct for which ones you think will appreciate long term?

Mathematically, it looks like the numbers work.