[x0x0]

You skipped entirely over trusts. Property managers are regularly not named members of an LLC. To wit, I'm a manager of an apartment building that I (quite unfortunately) don't have any ownership interest in. Building a state-by-state, or county-by-county lookup system; verifying person X is authorized to make decisions for a property; then detecting updates is decidedly non-trivial. You can skip googling since I already know the answer: there's very limited information available in many states on corporations. See eg Delaware. Other states don't require updates, or require updates only on very long periods. Many small LLCs simply skip even required annual updates. There's also complications such as the address used by the building and even the postal service is quite possibly not the recorded address. In 2015, [1] claims there were 550k property listings in the US alone. None of this can't be done, but trivial it isn't. I happen to know much of this because I used to work on address information.

[1] http://blog.airdna.co/2015-in-review-airbnb-data-for-the-usa...