Just because something's right mathematically doesn't mean it's right for you mentally.

The answer to this question lies in the mathematics.

The bank could foreclose if you have a mathematical/technical violation of your cash flow but they wouldn't be in the lending business very long if that was their goal.

Mathematics) and depth / expertise (e.g. 

A strategy is a mathematical equation that is applied to a way of moving cash and credit towards the goal of making a profit,...no and in the future. 

Money in VS money out in solid market areas.The challenge is that most people, including realtors, are not seasoned and great at mathematically doing the work of calculating returns and analyzing potential... accurately.

STEM fields - those in the areas of science, technology, engineering, and mathematics - are critical for the U.S. to remain competitive globally.

And even if they did it he HELOC would only be up to 70% of the property value, which doesn't work for me mathematically right now.

The way you prevent that situation is you figure out what prevailing rents are in your area and you price your rents accordingly.This is not to say that you rent your unit for the mathematical average of rent in your area for a unit of similar square footage.

Owning your primary "free and clear" may not be the best move mathematically/tax wise but it might feel awfully good :)Having cash on hand is great, and you have room to leverage more comfortably if you wish.