"A rich man is nothing but a poor man with money” means that people are the same; having more or less money doesn’t make one a better person. The saying has been frequently attributed to comic actor W. C. Fields (1880-1946), but it’s uncertain if he ever said it.
“It has been said that ‘a rich man is only a poor man with money’” was cited in a newspaper advertisement for the Bank of Montreal in October 1945. In May 1950, “a rich man is just a poor man with money” was called an “old proverb.”
Google News Archive
12 October 1945, The Buckingham Post and Papineau County Echo (Buckingham, Quebec), pg. 4, col. 2 ad:
What makes a little farm
a BIG FARM?
It has been said that “a rich man is only a poor man with money”.
(Bank of Montreal—ed.)
14 May 1950, Long Beach (CA) Independent, “No One’s Fault” (editorial), pg. 20-A, col. 1:
There is an old proverb, “a rich man is just a poor man with money.”
14 November 1953, Springfield (MA) Union, pg. 8, col. 3:
The late W. C. Fields had an apt definition of a rich man. He said a rich man was nothing but a poor man with money. If you follow the thought behind this quip, it makes it easier to remember the very slight line of division between comparative wealth and poverty and to retain a mental equilibrium when surrounded by novel luxuries.
19 August 1958, Rockford (IL) Register-Republic, pg. 12B, col. 1:
A RICH MAN is nothing but a poor man with money.
-- W. C. Fields
The Mammoth Book of Zingers, Quips, and One-Liners:
Over 10,000 Gems of Wit and Wisdom, One-liners, and Wisecracks
Edited by Geoff Tibballs
New York, NY: Carroll & Graff
A rich man is nothing but a poor man with money.
The Quotable Billionaire:
Advice and Reflections from and for the Real, Former, Almost, and Wanna-Be Super-Rich...and Others
Edited by Steven D. Price
New York, NY: Skyhorse Publishing
A rich man is nothing but a poor man with money. — W. C. Fields