Bet your bottom dollar
If you bet your bottom dollar on something, you are absolutely certain of it.

  "Jack is very punctual.  You can bet your bottom dollar he'll be here
  at 9 o'clock on the dot."


Cost an arm and a leg.


  If something costs an arm and a leg, it is very expensive!
  "The house cost us an arm and a leg, but we have no regrets."



Tighten your belt.  

If you need to tighten your belt, you must spend your money carefully.

  "Another bill?  I'll have to tighten my belt this month!"



Other side of the coin

  When you want to mention a different or contradictory aspect of a
  situation, you refer to the other side of the coin.
  "The house is lovely and spacious, but the other side of the coin is that
  it is far from shops and schools."



Go Dutch

   To go Dutch with somebody means to share the cost of something,
  such as a meal or a concert.
  "Young people today tend to go Dutch when they go out together."



Feather your nest

  To say of someone that they are feathering their nest is to say that
  they are taking advantage of their position in order to obtain money
  so as to have a comfortable life.


Feel the pinch

  When someone feels the pinch, they begin to suffer from a lack of
  money.
  "With the drop in tourism, hotels and restaurants are beginning to
feel the pinch."


Hard up

  If you are hard up, you have very little money.
  "We were so hard up we had to sleep in the car."



Keep your head above water

.   To keep one's head above water means to try to survive
  by staying out of debt, for example a small business.



On the house  

Something which is "on the house" is offered free of charge,
  usually in a bar or restaurant.
  "The new owner offered us a drink on the house."



Live beyond one's means  

If someone lives beyond their means, they spend more money
  than they earn or can afford.
  "The cost of living was so much higher in New York that he was soon
  living beyond his means."



To make ends meet.  

To make ends meet means to have enough money to live on.
Look/feel like a million dollars   If you look/feel like a million dollars, you look/feel extremely good.
  "With a tan and a new hairstyle, she looked like a million dollars."



Money burns a hole in your pocket  

To say that money burns a hole in somebody's pocket means that
  they are eager to spend it quickly or extravagantly.  
  "As soon as she's paid she goes shopping.  Money burns a hole in her
  pocket!"




Money to burn  

People who have money to burn have so much money that
  they can spend it on anything they want.



Money doesn't grow on trees

   To say that money doesn't grow on trees means that it is not
  plentiful or easily obtained.
  "Be careful how you spend your money David.  It doesn't grow on trees
  you know!"


Put money where your mouth

is  To put money where your mouth is means to give financial support
  to activities or causes that you believe are right.



Money talks

  Money talks means that people with a lot of money have power
  and influence.



Be paid peanuts

  If you are paid peanuts, you have a very low salary.
  "Anne has a very interesting job but she's paid peanuts.  
  Her salary is very low. "


Pick up the tab

  If you pick up the tab, you pay the bill or pay the cost of something.
  "There was a celebration lunch for the group and Bill picked up the tab."



Pretty penny

  If something costs you a pretty penny, it costs you a lot of money.
  "That new car must have cost him a pretty penny!"



Price oneself out of the market

  If you price yourself out of the market, you charge such a high price
  for your goods
  or services that nobody buys them.
  "He was so eager to make money that he priced himself out of the
  market."



From rags to riches

  If you go from rags to riches, you start off being very poor and
  become very rich and successful
  "By renovating old houses in the right places, he went from rags to riches."



Rake in the money  

If you rake in the money, you make money in large quantities.
  "Bob's business is so successful, he's raking in the money."




Rob Peter to pay Paul  

If a person robs Peter to pay Paul, they pay one debt with money
  borrowed from somewhere else, thus creating another debt.
  "David borrowed money from a friend to cover his overdraft;
  a typical case of robbing Peter to pay Paul!"




On a shoestring  

If you do something on a shoestring, you do it with very little money.
  "When I was a student I lived on a shoestring."