Our exterminator has a dog that can sniff for BBs. 

Find deserted, run down looking houses and contact the owners, etc....You are now describing a scenario of why no one needs agents any longer where Bird Dogs and Wholesalers are of more value. 

For example, I mention that every adult must pay a $30 application fee, pass my credit/criminal background, make a combined income of 3x the rent, and whether or not the property accepts pets.

They talked of pets and children to be much more common, meaning damage.

I would simply have left a welcome kit for each renter that included some shelf paper, toilet paper, and a new milky white shower curtain, plus a small bag of Purina if they have a pet.

As a guest of almost 50 STR stays, one roll of TP per bathroom is a major pet peeve of mine!

A warehouse building that was turned into a dog training facility and show place.  

Consider all the things that could go wrong and see if the lease addresses them: unauthorized pets or tenants, early termination, security deposit, lease violations, late rent, eviction, lawn maintenance, parking, etc.5.

For me when I'm estimating rental income I start by looking at the area for active listings <40 days old with similar characteristics to the home you're looking at purchasing (trying to find same bed/bath count, and same amenities like in CO homes with a fenced yard do very well because everyone has a dog).

How they've been in the property for 2 months storing their dogs there with no rehab movement, while putting sweat equity into it, but haven't addressed the foundation or any rehab issues yet.