Rule #1: You must know the difference between an asset and a liability, and buy assets.
If you want to be rich, this is all you need to know. It is rule number one. It is the only rule. This may sound absurdly simple, but most people have no idea how profound this rule is. Most people struggle financially because they do not know the difference between an asset and a liability.
“Rich people acquire assets. The poor and middle class acquire liabilities that they think are assets,” said rich dad.
…
An asset is something that puts money in my pocket. A liability is something that takes money out of my pocket.

Excerpt From: Robert T. Kiyosaki. “Rich Dad Poor Dad.”