Billionaires are known for throwing their money at super yachts, oceanside mansions, and luxury cars—but some still carry their thrifty habits made before reaching 10-figure net worths. Bill Ackman, the Pershing Square Capital founder worth $8.4 billion, still lives by his family’s money philosophy long after reaching the ultra-rich list.

“I don’t like wasting money,” Ackman recently told the WSJ. “Dad was very big on not wasting things. If I left my light on in my room, he’d get really upset. Now I go around the house turning off every light.”

Ackman is known to many as a controversially outspoken and powerful hedge fund success whose influence has spanned across politics and the business world (Ackman even credited himself to helping President Trump get elected). But long before his investing highs and amassing an X following of 1.8 million people, the now-59-year-old had a relatively normal home life. Born to commercial real estate broker Larry Ackman, the family lived in a $56,000 New York state house that Ackman said was a “stretch” for his dad to afford in 1965.

Knowing his family wouldn’t be passing down any inheritance to him, the hedge fund mogul paved his own path towards billion-dollar success. But that doesn’t mean he’s changed his tune on spending—he’ll go great lengths to score the best deal, even if that means driving around town just to find a cheaper place to park.

“If I don’t like the price of the garage, I’ll go to a different one. It’s funny. I don’t like paying for parking, and I used to own a parking company,” Ackman continued. “Or it really upsets me if the gas grill was running over the weekend—which it was, and it pissed me off. I really don’t like wasting money. I wouldn’t call it a neurosis, but it’s something that I care about.”

Other billionaires and entrepreneurs who are careful about their spending

Ackman isn’t the only billionaire saving money on the basics; Warren Buffett, the 11th richest person in the world with $148 billion to his name, still lives in the same Omaha home he bought for $31,500 back in 1958. Buffett also once drove a 20-year-old car because he felt it was safer than being behind the wheel of a flashy Lamborghini or Aston Martin, and is known for frequenting McDonald’s for a cheap meal—even whipping out coupons to cover the bill.

“I do not think that standard of living equates with cost of living beyond a certain point,” Buffett said at a Berkshire Hathaway shareholders meeting in 2014. “My life would not be happier…it’d be worse if I had six or eight houses or a whole bunch of different things I could have. It just doesn’t correlate.”

And Scale AI’s Lucy Guo, the youngest self-made woman on the planet worth $1.3 billion, echoed the same sentiment as Buffett and Ackman. The college dropout turned unicorn entrepreneur still drives her beat-up Honda Civic and makes her money stretch with buy-one, get-one-free deals on Uber Eats. When it comes to fashion, Guo has some designer dresses lying around for special occasions—but in her typical daily life, she only wears free clothes or cheap styles from fast-fashion brand Shein.

“I don’t like wasting money,” Guo told Fortune earlier this year. “Who you see typically wasting money on designer clothes, a nice car, et cetera, they’re technically in the millionaire range…All their friends are multimillionaires or billionaires, and they feel a little bit insecure, so they feel the need to be flashy to show other people, ‘Look, I’m successful.’”

Even successes outside the lucrative worlds of investing and AI are pinching their pennies. Actress Keke Palmer became a millionaire at the age of 12 and has continued to amass her wealth from hit Hollywood projects like Nope, Hustlers, True Jackson, VP, and One of Them Days—but you won’t catch her balling out. The star doesn’t “play around” with saving money and living frugally: something her parents instilled in her from a young age.

“I live under my means. I think it’s incredibly important,” Palmer told CNBC in an interview earlier this year. “If I have $1 million in my pocket, my rent is going to be $1,500—that’s how underneath my means I’m talking. My car note is going to be $340. I don’t need a [Bentley] Bentayga, I’ll ride in a Lexus.”

Billionaire Bill Ackman says he doesn’t like ‘wasting money’—he’ll even drive elsewhere for cheaper garages, despite once owning a parking company