gravy train, ride the
Experience excessive ease, success, or profit, especially undeservedly. For example, Now that his brother is paying all his bills, Jim is riding the gravy train. The word gravy has long meant “easy profits,” and the term is believed to come from 19th-century railroad slang, although the earliest recorded use dates from the early 1900s. W.C. Handy used it in one of his famous blues songs written in 1914, in which he bemoans falling off the gravy train. Also see easy street.