From Longman Dictionary of Contemporary Englishgravy trainˈgravy ˌtrain noun → the gravy train
Examples from the Corpus
gravy train• Six cents an hour, in Salvador, is considered the gravy train.Gravy TrainGravy Train trademark a type of dog food sold in the USFrom Longman Business Dictionarygravy trainˈgravy train noun [singular] informal disapproving1a business or activity where people can make money or profit without much effortThe question is how, in otherwise very competitive capital markets, this gravy train has survived so long.2a government organization where people can get jobs and earn money without working much or at all, for example because they know the right peopleMr Cardenas has campaigned strongly against corruption, warning that his government will not be a gravy train for his party’s supporters. 