Here’s how: 1. Find your S&P 500 index fund. It’s actually easy to find an S&P 500 index fund, even if you’re just starting to invest.. Part of the beauty of investing in index funds is that And the sooner you start investing, the more compound growth works to your advantage. Here’s what I mean: Let’s say you start investing $800 a month in good, growth stock mutual funds when you’re 35. If your investment grows for 30 years at the historic average annual rate of return, you could have over $1.7 million when you retire. The profit you get from investing money. Over time, this profit is based mainly on the amount of risk associated with the investment. So, for example, less-risky investments like certificates of deposit (CDs) or savings accounts generally earn a low rate of return, and higher-risk investments like stocks generally earn a higher rate of return.