I think of retirees, people down on their luck, and the occasional bad person.

@Chris Bird It can make sense in so many scenarios, but always requires an awareness of all the moving parts and, occasionally, a crystal ball.

I would during the course of the next inspection take a gander for any overt signs of more than an on occasional tenant and if I saw enough (More than some clothes and a toothbrush) I would simply inquire as to if she has added a tenant and inform her of what is required if that person takes up residency.

And I do get the occasional organic lead, which is a major achievement in this market.  

And then there their special "connections" access (remember James Garner's Rockford character would occasionally call his cop buddy 'Dennis' for info favors).I've used two or three PI's with some success over the years.

Don't be surprise when people occasionally offer to gift you a house, typically just about the time you are about to give up.

Your profile says you occasionally flip houses when time permits.

I occasionally get asked if I'm a Realtor/Agent & I'm always open about it, so these people that complain to my broker without calling me first irk me, especially when it's another agent/broker. 

Hey Mike - I occasional "get" to listen to some pretty crude characters, however it think your caller used F*** enough times to convince me of two things and one opportunity:1) The F word, when used as an adjective, loses its effectiveness and impact when repeatedly used (like very, very and many, many) in the same sentence as both a descriptor and as an end result.

When I was looking around here, you'd occasionally see a really big house that popped up.