Amanda Han (CPA) touches on this peripherally in the last podcast.  

They are most ideal when you have a lot of rooms  All you're gonna get is undesirables.

In other words, in New York, an applicant for an apartment can tell you that he or she is planning to live in the apartment by his or herself, go through and clear your background check, move in, and then permit another person with a criminal record (or any other undesirable rental history characteristic) to move in. 

As many people have implied, only law-abiding citizens will heed your ban on firearms, and the armed undesirables will ignore it and keep their guns.  

I know I can FHA the property, but the good deals would force me and my wife to move to the straight up undesirable areas.

Low demand/undesirable areas=low prices.

I’ve always heard to stay away from these types of properties, because they are undesirable to tenants.

Let's take your "undesirable areas" for instance.

It's ironic, becasue this struggle is what usually sends new investors searching for cheap properties in undesirable neighborhoods or cities that are dying.

He dropped all his undesirable freelance work, but he might pick up something like that.