I've been going with a nominal 10% based on the performance from some of my other properties, which admittedly could have been pure luck.  

So I think this is somewhat of a regional question like Jon alludes to.However I always look at personal residence separate from business and I buy purely on emotion.

The last guy was under contract but couldn't get financing, maybe this is part of the reason why, but that's purely speculation.

It's all pure fantasy.

As we started to progress we bought pure rentals and have continued ever since.

Of course it's pure speculation on his part but he's a 40-year resident of Durham with a lot of connections within the local government for what it's worth. 

They were bought as pure rentals.

Purely price negotiation through a back-door route...

It would take some policing to keep it on topic but with some reasonable rules, it could be really interesting data and far more helpful than pure stats or outlets like City-Data that tend to be overrun with biased lurkers.  

Jay has a good point, it's an NPN craze and it is purely driven by brokers marketing, guruized programs and misconceptions of great returns.