6 people who became millionaires by 30 reveal their keys to success

Mark Zuckerberg changed the way we communicate with Facebook, and as co-founder and CEO of the social media platform, he became a millionaire at age 22 in 2006. By 23, he was a billionaire.

In a 2016 Facebook post discussing the 10th anniversary of the platform's News Feed — and initial resistance to the feature — Zuckerberg lauded his team's willingness to take risks: "One of the things I'm most proud of about Facebook is that we believe things can always be better, and we're willing to make big bets if we think it will help our community over the long term. News Feed has been one of the big bets we've made in the past 10 years that has shaped our community and the whole internet the most."

Microsoft co-founder Bill Gates hit the millionaire mark in 1981 at age 26, and he became a billionaire by 31.

In a 2007 commencement address at Harvard, Gates discussed how complexity stands in the way of solutions: "The barrier to change is not too little caring; it is too much complexity. To turn caring into action, we need to see a problem, see a solution, and see the impact. But complexity blocks all three steps. … If we have clear and proven answers anytime an organization or individual asks, 'How can I help?,' then we can get action and we can make sure that none of the caring in the world is wasted."

The founder of Spanx, Sara Blakely, was 29 when she became a millionaire in 2000. Just over a decade later, she joined the billionaire's club at age 41 - becoming the youngest self-made female billionaire.

She is no stranger to failure and believes it's essential to success, telling CNBC in 2013: "My dad growing up encouraged me and my brother to fail … It's really allowed me to be much freer in trying things and spreading my wings in life."

In 1960, the business magnate, investor, and CEO of Berkshire Hathaway became a millionaire at age 30. By age 56, he was a self-made billionaire.

It's important to measure one's performance not just internally but externally, against the broader market, he told Inc: "Whether we do a good job or a poor job is not to be measured by whether we are plus or minus for the year. It is instead to be measured against the general experience in securities as measured by the Dow Jones Industrial Average, leading investment companies, etc. If our record is better than that of these yardsticks, we consider it a good year whether we are plus or minus. If we do poorer, we deserve the tomatoes."

Elon Musk, founder of SpaceX and cofounder of PayPal and Tesla Motors, reached millionaire status at age 27 in 1999 and then billionaire status by age 41.

During a 2014 commencement speech at the University of Southern California, Musk told students: "I think the first is you need to work, depending upon how well you want to do and particularly if you're starting a company, you need to work super hard. So what does super hard mean? Well, when my brother and I were starting our first company instead of getting an apartment, we just rented a small office and we slept on the couch. We showered at the YMCA, and we were so hard up we had just one computer so the website was up during the day, and I was coding at night—seven days a week, all the time."

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