You are not in uncharted territory.

Commercial zoning is essentially the difference between accommodating nightly tenants and being subject to the rules of the territory. 

If the animal is higher risk (cats, animals owned less than one year, dangerous breeds) then I charge additional fee up front before the animal ever moves into the property.

While still technically in seller’s market territory, inventory is well above extreme lows seen in recent years.

Property managers may be good sources of info for what neighborhoods are generally good and those which are dangerous.

I disagree and have supporting examples of the possible dangers to others, especially newbies, who might agree with you and think anyone with plenty of RE experience is good enough to take advice from.

That said, I believe any training classes give you enough information to make you dangerous.  

Once you adopt the premise that there is no rent advantage to a nicer / bigger B class property... the most lucrative place to put your money is where you will spend the least amount for the property, down to the point that the other negative "D class factors" override that formula (dangerous neighborhoods, drugs, and the other "looks like / smells like crap" comments the original poster mentioned.  

The one caution I would give is that there are some very good areas and some incredibly dangerous areas in which to invest. 

Long term deals can be dangerous, individuals or under funded entities are subject to life events that don't impact larger institutions or entities.