They say it’s not your crises that define you; it’s what you do with them. That’s the way it’s been with young superstar West Coast real estate agent Josh Flagg.

“One day, right in the middle of showing a client’s house, I fell in the pool,” he confesses. “I couldn’t let that slow me down, so I put on the owner’s robe, threw on some slippers and continued the showing.”

You could imagine the late-era Cary Grant mustering such aplomb, perhaps. But a guy who graduated from Beverly Hills High in 2004? Yet Flagg—whom you may have seen as one of the original regulars on Bravo’s reality TV series Million Dollar Listing Los Angeles—isn’t just unflappable. He’s the genuine article when it comes to real estate expertise, conviction, persistence and plain hard work. How else could he have sold more than $1 billion worth of properties before age 30 (a milestone he reaches this August), including the priciest homes in Los Angeles’ upscale Brentwood neighborhood and in Beverly Hills?

Maybe it’s the fact that he started selling real estate while still in high school that explains Flagg’s continuing penchant for doing his homework. “You have to know your market,” he says. “Really know it. I know what every home in my market sells for, who owns it, what they paid, who owned it before that and what they paid.”

Flagg has worked with celebrities including two Grammy winners—singer Adele and Adam Levine of the band Maroon 5—and record producer Steve Aoki. And he’s the author of two books, 2011’s Million Dollar Agent: Brokering the Dream, and A Simple Girl: Stories My Grandmother Told Me, published two years earlier.

That grandmother, by the way, was the late Edith Flagg (1919–2014), a renowned fashion designer and executive who was the first to import polyester to the U.S. for use in clothing. And the resourceful World War II Holocaust survivor and Dutch resistance fighter bequeathed more than genes to her grandson. The pair, who often traveled together, shared similar values, discipline and pluck. One time Edith even put in an appearance on Million Dollar Listing Los Angeles with Josh.

“She was extremely hard-working and passionate about her work, and I am too,” he says. “The fashion industry and real estate are not that different.” In fact, one of Edith’s business precepts arguably applies even more to his industry than to hers.

“She always said, ‘You don’t want to make one sale—you want clients for life,’” Josh recalls.

Today he keeps his grandmother’s spirit alive in his own frequent journeys. “I travel three months out of the year,” says Josh, whose favorite spots are southern France and southern Italy. “Travel is one of the best educations I could imagine—better than college.”

One thing travel teaches, of course, is that two distant places with different topography, foliage and climate can actually be kindred—like Beverly Hills and the Hamptons. Thus Josh Flagg and Jon Davis, both young superstars in their respective high-end markets, have worked together, referring clients to each other and helping each other with sales. “L.A. isn’t quite as expensive as people think,” says Josh. “The Hamptons are actually higher. But they’re also seasonal. We’re lucky in L.A. with our weather.”

Besides being similar—both known for their can-do attitude, stellar reputations and relentless commitment to their clients—Josh and Jon are good friends. “I love the Davis family,” says Josh. “We’re very close. And Jon and I are the two best real estate agents anywhere!”

Oh, and that interrupted showing, when Josh fell in the pool? Turns out he did make the sale.