[DamnYuppie]

After calculating your taxes I would do something kind of nice for yourself and after that put the rest and put it away in an index/mutual fund.

[zozbot234]

The nicest thing OP could do for themselves if they've "never had this kind of money in the bank" is build a rainy-day fund. It can save them a lot of stress down the line. For that matter, depending on employment situation and the like, it's not even unheard of for people to keep one year's expenses or more in highly liquid rainy-day/emergency funds.

[tinyjackpot]

I don't have _any_ debt.

Which index should I use? What are the differences between using an index and a mutual fund?

[GaryNumanVevo]

A stupid simple approach: use a Boggle 3-fund portfolio [1]

[1]: https://www.bogleheads.org/wiki/Three-fund_portfolio