re: If you received $500K, how would you invest it?

Get to know a rich multi millionaire and see what they are investing in and see if he will let you invest also. make sure he is investing much more than you. I stay out of market unless it is an IRA. just much more money to be made with smart rich people who know what they are doing.

Obviously don't put it all into one investment but find 3-4 different investments like healthcare, oilfield, real-estate...

Healthcare is booming right now so if you find the right product like an urgent care center or corporate medicine then it is pretty much a no brainer.