I've seen this play out. My parents rent houses in a community with two large college campuses within 30 minutes. A group of students or recently graduated newly employed would approach my Dad. Most of the time he wouldn't even consider it -- even if the leaseholder could credibly make rent on their own.

And in some zoning designations, this is actually illegal. For example, years ago I lived in a house in the same town with 4 other guys, but it turned out the maximum number on non-related people allowed in a "single family" dwelling there was 3. The landlord let everyone move in but eventually threatened to kick us out on those grounds.