[jonknee]

> The rest of the listings are from MLS systems and they pull housing data from county systems. For that, I'd assume there is a data broker and Zillow isn't integrating with thousands of counties.

That's not the case, MLS is a giant mess and the reason why Zillow was/is amazing is that it aggregated and normalized lots of different unconnected systems. They still have gaps and it's common for an individual MLS to play hard ball and not give out their data, but it's still a large competitive advantage.