What rate of return should I expect in the long run in an index fund?

In a growth index fund, such as the S&P 500, it's safe to ume a 10-12% annual return over the long haul. If you add $300/month for the next 40 years, you'll end up with around $3 million, conservatively. Even with the inevitable Obama-induced hyperinflation to come, you'll probably still be pretty comfortable.