Homeless people live on rocks.
Non-homeless people live in rocks.
Rock Residences
Explanation
Explain Bear
Hey, chucklehead! This "joke" is trying to be clever by contrasting where homeless people live (on rocks) with where housed people live (in houses, which, get it, are made of rock). It's about as funny as a screen door on a submarine, which, knowing you, you probably think is a GREAT idea.