Today's teacher tell me many idioms!
bread and butter - one's income, the source of someone's food
e.g. )The man's business is his bread and butter and he works very hard to make it successful.
bring home the bacon - to earn the family living, to earn a salary
e.g.) I have been working hard all month bringing home the bacon for my family.
chicken feed - a small amount of money
e.g.) The amount of money that I paid for the used car was chicken feed.
very interesting ;)