Guy, an interesting read, but I totally disagree that the solution is more government regulation or oversight of rental properties - unless they are part of section 8 and are therefore offering a service in exchange for income.
IMO, the answer to your question of "When would you know....." is more based on personal integrity and ethics than a hard or fast "model". Many years ago, we had a real estate investor in Tulsa, who was so motivated by greed that he did some very unethical investing. Like Mr. Gatley, he ended up losing everything in bankruptcy. The stories his tenants told, while not as bad as this article states, were still pretty sad.
As I was interested in starting my SFH business, I actually interviewed this guy (a couple of years before his empire crumbled) to find out how he was able to build what seemed like a nice empire. He told me how he was doing it. My question back to him was "how do you sleep at night and also deal with your conscience"?
Fortunately, I have built a nice collection of SFH in Tulsa, but I learned what not to do primarily by doing the opposite of what this guy did. While I'm not trying to come off as a hero, I do think that rental properties is not just about the physical assets you own, but more about the service you offer to your tenants. Unfortunately, there are tenants that will try to take advantage of that approach.
One last thing to offer, I have personally found the media tends to demonize landlords and make it seem like all tenants are victims. The Tulsa World recently did an expose on the high level of evictions in Tulsa County which very much had that theme of victimhood. So, I called the author of the article and he definitely had no idea what landlords deal with and admitted he had only done one side of his research when writing his article. To his credit, he did a follow-up piece talking about the causes of evictions and that included some references to "not paying your rent means the landlord can't afford to let you stay in the house or to keep the house in top notch condition".
Would enjoy reading anybody else's thoughts on this question. Thanks for asking it!