Renting in a small town - I think that is a good point. I've had family members that have rented in Wilber, but this has been a good 20+ years ago, but I think it's still true the POI's could have picked up a rental for pretty cheap. I think there is a reason they are renting the basement - in all likelihood, their Landlord may not ask many questions and that was part of the appeal. Also, they could maybe come and go with fewer neighbors observing them. My grandma used to joke in Wilber your neighbors know what time you use the bathroom, and if the POI's had a small house or apartment they would have neighbors who could be nosy and ask questions. They may have known their upstairs neighbors wouldn't ask questions.
As I keep saying, I think it is ultimately extremely strange no one seemed to have seen them at the bars, or at Casey's, or even at the Wal-Mart in Crete - or at least I haven't heard any local talk pertaining to sightings. If it's the case no one has seen them, then why were they so careful at keeping a low profile?