Mutual funds are a great choice for investors of any kind, beginner to advanced. They offer a way to easily diversify your investment, and you can do so at a very low cost. Those are two reasons they’re so often used in popular retirement vehicles such as 401(k) accounts or IRAs.A well-diversified mutual fund can be great for investors who are just starting out and know little about investing. In fact, investing legend Warren Buffett has long recommended that investors buy index funds based on the S&P 500 index, which can be done easily using mutual funds.