So you want to invest in the stock market, but you don't want to hand-pick specific stocks. Simply mirroring the S&P 500 (SNPINDEX: ^GSPC) market index can deliver fantastic results over the years, and you'll never lose a single night of sleep worrying about the rise or fall of any particular stock.

Sure, you can save up a bit more before buying these high-quality ETFs, or use the fractional share feature of your favorite stock brokerage to pick up 83% of an iShares or SPDR share for less than $500. But you actually have one more option. Meet the SPDR Portfolio S&P 500 ETF (NYSEMKT: SPLG) -- a fourth pure-play S&P 500 index fund that costs just $70 per share today.

This fund is exactly the same thing as one of the classic S&P 500 index ETFs. They hold the same 503 stocks, reflecting the components of the S&P 500 index. The weightings are identical. Their management fees are slightly different, with an annual expense ratio of 0.09% for the more famous S&P 500 ETF and 0.02% with the lower-priced Portfolio fund. But both offer the same performance as the underlying S&P 500 index, for all intents and purposes: