What specific details would they have that other's don't. I don't know how prevalent FSBO is on Zillow in some markets, but in mine it's extremely limited. I'd be shocked if it made up 5% of the residential market, probably closer to 1%.
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. If that's the case, then both the MLS and county data can be had by anyone. With that information, you'd get lot details, house details, listing history, county tax valuations and sales history.
What other data do you need?
A lot of house flippers are agents because they get the MLS listings ahead of the public and can move faster on them. I don't know when Zillow gets their MLS data, but listings almost always hit Realtor.com a day before they hit Zillow, so I don't see that as an advantage either.
