- Rob Gronkowski is retiring from the NFL with his entire career earnings: $54 million, according to Spotrac.
- He was able to save this nest egg by following a simple money rule: keep it simple by saving surplus money.
- Gronkowski previously told Business Insider he lived off only his endorsement earnings.
- Gronkowski is in good company — some of the world's wealthiest people, like Warren Buffett and Mark Zuckerberg, are known for having frugal spending habits.
Rob Gronkowski announced on Sunday that he would retire from the NFL.
The New England Patriots tight end has a nice nest egg to fall back on: his entire NFL career earnings, which total $54 million after nine seasons, according to Spotrac.
Business Insider's Scott Davis previously reported that Gronkowski, 29, hadn't spent any of the money he made during his NFL career, only his endorsement earnings. He advised other players to follow a similar plan and watch their spending overall.
"I'd just say keep it simple," Gronkowski told Business Insider last year. "Keep it easy, and I'd say keep it simple. Get what you need to be comfortable, save the extra."
He continued: "It's a short career here in the league. The average is about three to four years, and when it's done, it's done. Be simple, manage it safe, so when it's done you've got a little base, a little foundation to live off."
Gronkowski's savings strategy isn't far from the financial habits of other successful millionaires and billionaires, many of whom also live relatively frugal lifestyles.
Some of the world's wealthiest people live very affordable lifestyles
Frugal lifestyles help millionaires get rich in the first place, according to Sarah Stanley Fallaw, the director of research for the Affluent Market Institute and an author of "The Next Millionaire Next Door: Enduring Strategies for Building Wealth," in which she surveyed more than 600 millionaires in America.
During her research, she studied the characteristics most predictive of net worth and found that six behaviors, which she called "wealth factors," were related to net-worth potential, regardless of age or income. One of those is frugality: a commitment to saving, spending less, and sticking to a budget.
"Spending above your means, spending instead of saving for retirement, spending in anticipation of becoming wealthy makes you a slave to the paycheck, even with a stellar level of income," she wrote.
Read more:Rob Gronkowski is retiring from the NFL with $54 million after saving all of his career earnings
Consider Warren Buffett, who still lives in the modest home in Omaha, Nebraska, that he bought for $276,700 (in today's dollars). Richard Branson is famously frugal when it comes to buying luxury items, and several other billionaires, like Mark Zuckerberg and Jeff Bezos, have been spotted driving affordable cars — Hondas, to be exact.
Tyra Banks, who has an estimated net worth of $90 million, saved so much money that she was able to buy a house at 20 years old. Her accountants even told her she needed to spend money and had her set up a frivolous account.
Jay Leno, who has an estimated net worth of $250 million, had a strategy similar to Gronkowski's. He's said he always tried to hold two jobs, spending money from one while saving from the other. He saved all his money from hosting the "Tonight Show"— as much as $30 million a year — and spent only what he made from stand-up comedy.
When it comes to reining in your paycheck, it looks like Leno and Gronkowski are on to something.