money spinner	a business or product that makes a lot of money for someone
coining it/money	to be earning a lot of money quickly
licence to print money	to generate a lot of money without much effort
turn up like a bad penny	a person or thing which is unpleasant, disreputable, or otherwise unwanted
big bucks	lots of money
dime a dozen	said about anything that is common, inexpensive, and easy to get or availible anywhere
cost an arm and a leg	extremely expensive
ill-gotten gains	money or other possession gained dishonestly
make a fast buck	to earn money without much effort
money for jam	said about a job when it is an easy way of earning money