Should I put $10K into an S&P 500 index fund (VFIAX) and then put $25 a month into it after that?

$VFIAX is a Vanguard mutual fund. I personally hate mutual funds and prefer ETF’s instead, but realize when talking about a company retirement account, it may only be allowed to select mutual funds. $SPY is slightly different as an ETF — probably the most popular S&P index.

What’s the difference? Mutual Fund Vs ETF: Which is Right For You?

Auto-investing is a solid strategy assuming you want to grow your capital 20+ yrs from now. There will be peaks and valleys in your equity balance over many years.