Picking up rent even if it is not in cash cold very well attract undesirable attention and place you at risk.Please consider your safety.

And it's helpful in preventing undesirable activities from occurring on your property. 

That right there is reason enough to nip this cancer in the bud and get rid of these types of undesirables.

Whether you are a Section 8 property or not, you still want to get tenants who will pay rent and not damage your property, or cook meth in it, etc.If the only people who are willing to live in a property are criminals or undesirables, then you will have problems.So, no, not any property will be a good investment.  

On the positive side, all of the interior walls are concrete block which limits peripheral damage when shooting occur inside the buildings or tenants set their units on fire.

Stay under market if you have a undesirable property otherwise why would you supplement your tenants rent.

I use a standard scoring system.Find out if your insurance coverage disallows any breeds.You may end up needing to accept an undesirable animal, then you have to hope for the best and keep them accountable to the rules, damages, and quiet enjoyment for others.

I prefer month to month as it's easier for me to get rid of undesirable tenants and I don't like keeping people hostage as renters when it's super easy for me to find a new tenants as I offer below market rents in a hot market in order to attract better tenant that will comply with my explicit instructions of "not to bug me unless its an emergency." 

Most do not want to be in the hood or an undesirable area just like you and I don't.

This results in less rule breaking, less property damage and less undesireable behavior.Remember, it is like a chess game.