Ask HN: What are the easier ways to become rich than starting a startup?

Sam Altman mentioned in his first lecture of "How to Start a Startup" that "There are much easier ways to become rich and everyone who starts a startup."

What are those ways? Consulting? Investing in property?

I think he didn't think of specifically anything, he just wanted to emphasize how hard it is to build a startup.

Also, those who can answer this kind of questions are too busy getting rich right now.