Or is there something about your properties that makes them undesirable to good tenants who have more options?

Many companies require you to use their application forms (on-line or faxed/e-mailed), which we do and add our own supplemental pages for info they don't request but we want.Think about the qualities of a good tenant, what your criteria is, and design a process to weed out undesirables and look at credit, criminal landlord history.  

Renting to the older tenant means less turnover and no kids.And I disagree that smaller units are undesirable.  

I found this weeded out a lot of undesirables.  

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.

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." 

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

The property needs some tlc which is why it's a good deal but the small things that need to be fixed have made it "undesirable" to the 2-3 carriers that are left in this area willing to write rental properties.

Public transportation for mid-class working people seems to be mostly undesired, making the last point not as important IMO.