Money Money Money

Old money vs. New money has nothing to do with the age of the currency; it has to do with how long money has been passed down from generations. Old money is "the inherited wealth of established upper-class families" or "a person, family, or lineage possessing inherited wealth". Old money typically associated with the upper class. New money is recently acquired wealth, someone who has worked hard and earned their money rather than inheriting it.

In The Great Gatsby, Tom Buchanan is an example of old money. He inherited his family's money, not having to work for an income, simply inheriting the riches. Jay Gatsby is an example of new money. He has recently acquired wealth that he enjoys showing off in extremely luxurious ways, like throwing hugely extravagant parties.
The Rockefeller and Vanderbilt families are some examples of "old money". They have enterprised and kept their money, passing it down through generations.