[apple4ever]

But we have databases of addresses and we can tell if it actually has 1000 apartments.

[ill13]

Who's updating those db's when I turn my single family in to a tri-plex , then convert it to an 10 unit apartment complex?

The answer is "no one".

[Strom]

That depends on where you live. In my country the government keeps an up-to-date db. Everything else in the country depends on and queries that db too, so it's not isolated.