Answer by taking a quote from the following article:

Spitz was born in Modesto, California, the first of three children of Lenore Sylvia (Smith) and Arnold Spitz. His family is Jewish; his father's family was from Hungary and his mother's, originally surnamed "Sklotkovick", were from Russia. When he was two years old, Spitz's family moved to Honolulu, Hawaii, where he swam at Waikiki beach every day. "You should have seen that little boy dash into the ocean.

In 1972, soon after his return to the United States, Spitz landed several lucrative corporate endorsement contracts. He earned about $7 million in a two-year period. However, as the memory of his feats receded, so did his endorsement and promotional deals. As his endorsements faded he started a successful real-estate company in Beverly Hills. He bought a Ferrari and says he made more than $1 million. "A million dollars in 1972 would be equivalent to more than $10 million today," Spitz said. "I did very well, thank you very much." "I would say I was a pioneer. There wasn't anyone who'd gone to the Olympics before me who capitalized the same way on opportunity. It depends on timing, it depends on hype, it depends on the economy, and most importantly, it depends on looks. I mean, I've never seen a magazine of uglies. That's our society. I'm not saying it's right. That's just the facts."  Per his official website, Spitz is self-employed as a corporate spokesperson and motivational speaker. However, Sports Yahoo! lists his occupation as a stock broker and motivational speaker. According to a recent interview "Spitz became a stockbroker in 2002 and has since moved into private equity. He is now also dabbling in the "water business," as he calls it, and is in negotiations to build a water-bottling facility on aquifer-rich land that he and a business partner own.  He has pursued various entrepreneurial projects with former NBA player Rick Barry. He travels the world delivering about 25 lectures a year. His biography, The Extraordinary Life of An Olympic Champion by Richard J. Foster, was released in July 2008.  In July 2012 he endorsed Istanbul's bid to host the 2020 Summer Olympics.

When did his swimming career end?
In 1972, soon after his return to the United States, Spitz landed several lucrative corporate endorsement contracts.