re: How do I invest in the S&P 500?

Just buy an index fund that follows the S&P like FXAIX. There are several out there. Most 401ks have some option to choose to invest in an index fund that is a S&P 500 follower. Like Fidelity's is FXAIX, etc. Or you can buy it with money in an IRA, monkey market, etc.

You can buy fractional/whole shares of it for whatever amount you want.