In five years, Grant Sabatier of "Millennial Money" went from having $2.26 in his bank account to $1 million, thanks to a side hustle that he turned into a lucrative consulting company.
"As soon as I began this journey, I looked up the best-reviewed personal finance books on Amazon," the now 31-year-old tells CNBC Make It. Since, he's read over 360 personal finance books and "the best book on money, period," happens to be the first one he picked up: "Your Money or Your Life," by Vicki Robin and Joe Dominguez.
The 1992 classic, which was recently revised and updated, changed Sabatier's relationship with money and his approach to spending and saving, he says: "The premise of it is that you exchange your time for money. And when you start thinking about how many hours of your life it took to save up the money to buy something, you really start thinking twice about your purchases."
"Say I work eight hours a day and after taxes, make $10 an hour, meaning I'm earning $80 a day. I want to go out for a nice dinner on Friday and that costs about $80, meaning I spent an entire day of my life working for this meal. And then you start thinking about even larger purchases, like a $1,000 TV, and you think, 'How much of my life did I trade for this? Is it worth it?'"
He's not the only self-made millionaire who recommends the read. One New York City-based millennial who goes by the pen name J.P. Livingston on her blog "The Money Habit" retired with $2.25 million before age 30.
She had financial independence on the mind as a kid and picked up a copy of the personal finance classic "Rich Dad, Poor Dad" at age 12. The second money book she ever read was "Your Money or Your Life," which "opened my eyes" to the idea of early retirement, she tells CNBC Make It. "That book, the concepts of it really stuck with me. That was the one that actually, of the two books, really spurred things for me."
Then there's Chris Reining, who buckled down to focus on his finances in his late 20s and became a self-made millionaire at age 35. Robin's book is "the book that changed my life," Reining writes on his blog.
It introduced him to the idea of tracking his income, spending and investments in a spreadsheet and graphing his "cross-over point": when monthly investment income crosses above monthly expenses. "When this point happens is when you can seriously consider retiring because you are officially financially independent!" he explains. "No more income is needed from a job."
Turning your financial goals into something visual such as a graph is crucial, says Reining, because "it drives home the point that you can, in fact, retire early."
He tells CNBC Make It: "Once you start tracking this stuff and seeing it month to month and then year to year, you really start to understand, 'If I spend less, that means I'm saving and investing more. And if I'm saving and investing more, I'm going to be able to walk away sooner. I'm going to be able to have financial independence sooner, because these numbers all work together."
This is an update of a previously published story.
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