You can use Google Maps (GM) to measure out 3 miles from your target facility.

Become additionally insured on their general liability insurance policy, and for extreme measure, ask to get a performace bond in the beginning.

My assumption is I can get a HELOC within a year of the purchase, but please let me know if there are more stringent holding periods to qualify for a HELOC. 

Your occupancy at 85% is a good measurement for a stable property.

CoC is my main measure, but I use the 1-2% rule to decide what I want to consider researching further for rentals.

The more complex aspects include circumnavigating the security measures intended to prevent scraping from occurring.

Is there a device that I could hook into the box to measure all the electric used by the apartment and house and then just charge them or should I just eat the electric and push the rent up a little?

If not, as a conservative measure, you can use the land/building value split used by your tax assessor as the first step. 

You have to decide for yourself what metrics you want to use to measure acceptable investment return and to determine when you want to stop acquiring properties, and begin just reducing the debt on what you own with your eventual goal free and clear ownership. 

If you measure the totality of your investment, mean cash flow, debt reduction, appreciation, rent growth etc you will always make more money in the areas of high demand like DC, Boston, Seattle etc than you will make in a pure cash flow market like you will in the mid west.There is always the possibility of your rate going higher, but thats the trade off of a lower rate with the arm.