Money for jam/old rope
Definition 1 of 1
Pro Tip 1/3Informal Use
The phrase is casual and often used in friendly, informal conversations. 
When I told my friend about my side job, she said it sounded like money for jam.
Pro Tip 2/3Positive Connotation
The phrase generally implies a fortunate situation where someone benefits with little effort. 
He inherited a profitable business—it's pretty much money for old rope for him.
Pro Tip 3/3Not Always Literal
It's not taken literally. It means the task is very easy, not that you get actual jam or rope. 
She gets paid to watch movies all day; it's really money for jam for her.