The property was rented and generated $160 cash flow after mortgage, taxes, insurance and property management fees were paid.

Is anyone familiar with the rule listed in the title and is anyone that has a full-time job in another industry using this rule?

Additionally, I've been spending a lot of time evaluating condo / HOA management solutions and accidentally stumbled on ManageCasa, which offers a free trial and < 3 unit free tier that has allowed me the time to get in, kick the tires, and really appreciate their attention to detail and broad feature set that adapts to each unique industry sector.

This allowed us to maximize revenue and occupancy more effectively.Safely Insurance: We also decided to use Safely Insurance, which provides comprehensive coverage for guest damages, liability, and protection beyond what Airbnb or Vrbo offer.

It also negates the need for insurance - although that isn't our MO. 

Though I would caution you on hard money lending until you understand the industry a bit better, that can be very rewarding but you have to be able to do your due diligence on deals because you're turning over your hard-earned money to an individuals project, often a flip. 

That's $1,600 per month plus to pay debt, plus at least $400 in taxes and insurance.

Be sure to hold a hefty reserve to handle on-going maintenance, capex, taxes, and insurance.

Many insurance companies do not allow adding a landlord as additional insured.  

Not WAIT for the most popular platform in the industry to dump them all at the SAME TIME in the SAME PLACE AFTER they have been posted somewhere else first.Read my profile for further insight and  if you want the study I done I can post it here.