Originally (early 70s or so), a standard cliched response to the question "What's up?".  Then, in the late 80s/early 90s, a new generation misunderstood the origin of the response so that it soon became the standard reply to similar questions, such as "How ya doin'?" or "What's goin' on?"
Original:
Dude 1: What's up, man?
Dude 2: You know, nothin' but the rent.
Later:
Dude 1: Hey, man, how you doin'?
Dude 2: Aw, nothin' but the rent, man.
Dude 1: What's up, man?
Dude 2: You know, nothin' but the rent.
Later:
Dude 1: Hey, man, how you doin'?
Dude 2: Aw, nothin' but the rent, man.
by SteveRos July 5, 2005
 Get the nothin' but the rentmug.
Get the nothin' but the rentmug. A security guard who falsely accuses somebody of malfeasance or wrongdoing and stubbornly defends this assumption.
by James Conrad May 20, 2008
 Get the rent-a-Clouseaumug.
Get the rent-a-Clouseaumug. by Your pseudonym #100 May 28, 2015
 Get the Rent Boymug.
Get the Rent Boymug. by CannibalHannibal666 January 2, 2011
 Get the rent-boymug.
Get the rent-boymug. one who is easily persuaded to a side of opposition; one who is a douche or asshole to anyone and everyone, including Jesus Christ, himself
by they call me night hawk September 16, 2010
 Get the Rent-A-Bitchmug.
Get the Rent-A-Bitchmug. The ‘Rent Due Theory’ is a scientific phenomenon within women where every 25th to first couple days of each month women whine about men not providing for them for free.
by enfdoom July 26, 2023
 Get the Rents Duemug.
Get the Rents Duemug. Living in someone's head rent free. They are in your mind all the time and you are constantly thinking about them. All your thoughts are about them, and they have no idea. Usually happens when you have a big crush on someone
by TRISTANISANEXTREMESIMP October 25, 2020
 Get the Rent freemug.
Get the Rent freemug.