[dave5104]

Occupancy limits are somewhat common in many cities/towns. But probably only enforced via neighborly complaint, so you don't really hear about them.

Just searching "occupancy limits city" popped up the limits for Boulder, CO: https://bouldercolorado.gov/occupancy-limits

[zardo]

The kind of thing where you're fine unless you're "a problem" for one of your neighbors

A problem as defined by your nosiest, most uptight, or most xenophobic neighbor.

[panzagl]

Boulder is... special. A college town where a bunch of rich people decided to live. I've never seen a campus with so many non-students on it, just hanging out like they belong there or zipping through campus on their bikes at 40 mph. But most college towns have similar occupancy laws for neighborhoods where they want to keep students of the wrong sort out of.