Though not a bad idea, $100k cash is slowly being chipped away at with inflation every day. Due to how our financial system works, you are probably ticking off days of that decade yearly by leaving it in cash.
Invest it in index funds. That's pretty safe, and gives pretty good returns. The only way that's going to disappear is if the entire economy dies, and then money won't be any good either. If you want to prepare for that, you need to buy land.
Just to add, invest in broad-market index funds (or ETFs). Something which tracks FTSE All Worlds, MSCI World, maybe even S&P 500. Nowadays, there are hundreds of indexes that are so narrow I'm baffled how they're useful.
Absolutely. It's easy to get lost in the world of cryptic indexes. I generally use and advise S&P 500, because it's easy to find, remember and understand, and it performs very well.
I should probably look into MSCI World SRI, which is a socially responsible index (or a neverending collection of indices) that excludes all sorts of dirty and questionable enterprises like oil and weapons.
When you have 2300 ETFs in the US and 7000 globally, narrow indices are important ways to tailor your exposure as the broad index stuff probably has ten different vehicles to invest in..
