In the quest to find incredible growth stocks and become a millionaire investor, one often faces numerous challenges. The process of identifying the next big winner in the stock market can be incredibly difficult. However, renowned investor Warren Buffett has a simple solution that he both recommends and owns for his company Berkshire Hathaway: the Vanguard S&P 500 ETF.

Many investors dream of achieving a $1 million stock portfolio, seeing it as a significant milestone and a source of financial security for retirement. While there are various ways to reach this goal, finding the next Nvidia or similar high-growth stock is akin to finding a needle in a haystack. Moreover, the risk associated with singling out a potential winner can be substantial.

The simpler and more reliable approach to becoming a millionaire investor, according to Buffett, is to invest in the entire haystack by buying an S&P 500 index fund. Buffett favors Vanguard funds and specifically holds the Vanguard S&P 500 ETF (VOO 0.79%) through Berkshire Hathaway.

Consistently investing in the Vanguard S&P 500 ETF is regarded as one of the surest paths to building a $1 million investment portfolio. While it may lack the glamour and rapid growth potential of individual stocks like Nvidia or other AI-driven companies, an S&P 500 index fund offers attractive long-term returns and diversification within a single investment.

Even if investors believe they have found the next Nvidia, concentrating a major bet on a single company carries substantial risks. Alternatively, building a well-diversified portfolio of individual stocks and other assets in the hope of reaching $1 million requires significant time and effort spent researching and staying updated. For those who value simplicity, an S&P 500 index fund can serve as a one-step solution.

Investing in the Vanguard S&P 500 ETF produces returns that closely mirror the performance of the S&P 500, historically averaging a compound annual total return of approximately 9.8%. Based on this figure, it is possible to estimate how much investors need to contribute monthly to reach a $1 million portfolio over time.

While the Motley Fool's Premium Investing Services may have differing opinions, the Vanguard S&P 500 ETF stands out as an appealing option for aspiring millionaire investors seeking consistent and predictable returns. Following the advice of legendary investor Warren Buffett, investors may find that simplicity, long-term growth, and diversification are key factors in building their wealth over time.