kate_sept2004 / Getty Images Market-matching returns, minimal fees, and compounding together make index funds one of the most reliable paths to building wealth. Key Takeaways Index funds consistently outperform actively managed funds. They also cost less and can work better tax-wise. Index funds invest in a bucket of stocks that represent a part of the stock market, like the S&P 500. Many dream of retiring early, but achieving that goal doesn't require high-priced financial advisors or complex inv ...