If you're going to invest in index funds (and you should), don't pick the S&P 500. Why invest in 500 stocks when you could use the vanguard total market index instead, and invest in essentially the entire US market, with a management fee of 0.05% per year? Also, there's no need to take on unnecessary risk by concentrating investments in the US. Better to put a good portion in a broad ex-US fund as well. Vanguard has a good option there too, of course, but there are certainly others as well.

Also, if like me you're outside of the US, these all come in ETFs that can be bought anywhere and have similarly low fees.