Shark Tank's Kevin O'Leary Reveals the Riskiest Investment Mistake People Make in Their 20s

Kevin O'Leary, aka Mr. Wonderful, explained in a recent post on the social media platform X that young people in their 20s who invest their money often make the riskiest mistake of putting all their eggs in one basket.

'Everybody thinks they've found some hot stock or great idea, or they're going to start a restaurant or something, and they take all of their money and commit that big mistake,' the investor said.

According to the Shark Tank star, the key to success in investing is recognising from day one that 'you are going to make mistakes,' which makes portfolio diversification essential. When a stock 'goes to zero', it does not wipe you out entirely if you have spread your risk.

O'Leary's Thumb Rule For Diversification

O'Leary advised young investors to spread their investments across various industries and companies to avoid concentrated risks. His simple strategy is to never allocate more than 5% of your portfolio to a single stock.

'Never put more than 20% in a sector or 5% in a single stock. When poo hits the fan, you want to survive,' he wrote.

In 2025, O'Leary criticised Gen Z's spending habits, describing habitual expenses like spending $28 (£20) on lunch while earning $70,000 (£51,988), which he sees as a barrier to wealth accumulation. He added that such money could be invested in long-term index funds to build wealth. He also urged young investors to buy homes only if they plan to stay long-term.

O'Leary Shares the Fastest Way to Make $10K from Scratch

In a separate post on X, O'Leary said that if he had no money tomorrow and needed to earn $10,000 (£7,426) in a month, he would sell customer acquisition services via social media. Instead of panicking or chasing luck, O'Leary would leverage digital access to create cash flow.

Although millions are attempting to turn their phones into money-making machines by creating reels and clips to monetise their content, hoping the algorithm will boost their rankings, O'Leary notes that the segment has become too crowded.

However, he wouldn't try to be seen but would focus on being needed. He would create content quietly, sell directly, and refine his strategy to ensure the business grows through usefulness. His approach of leveraging one simple, effective tool—rather than chasing trends or a large audience—is what makes this method work.

'Just with your phone—if you know how to edit video and post it on social media, you can acquire customers,' he explained.

The entrepreneur said that people can walk into businesses and offer to help them bring in customers for $100 (£74) each. 'You'd be amazed at how many business owners have no idea how to use social media. And if you've grown up with a phone in your hand, you do,' he noted.

O'Leary believes this strategy is 'the number one source of income when you're really looking for something to make money,' describing it as the 'best side hustle there is.'

Disclaimer: Our digital media content is for informational purposes only and does not constitute investment advice. Please conduct your own analysis or seek professional advice before investing. Remember, investments are subject to market risks, and past performance does not guarantee future returns.