One of the first recorded uses of the word Parentals was used in the film "Bring it on" in 2000:
"I can't mack on you in front of the parentals" so the shortened version "Rentals" is likely to have come into circulation after that time.
2.Awrite mate u comin daan the chippy or did ya rentals graand ya agen?
"Lets not go to Ponderosa, I like to buy my food, not just rent it for 15 minutes."
not to be confused with 'loaner',wherein your naive best friend has to go out of town and entrusts you to keep his girlfriend "safe and entertained",but of course you fuck her,because the pent-up sexual tension is more than either of you can handle... but i digress.
"aw naw,man,that was just a rental."
"whenever I'm visiting a new town, I always get a rental."