If I were you, I would suggest to him that he invest all except 4% of it, in a combination of the following
Vanguard Total Stock Market Index Fund Admiral Shares (VTSAX)
Vanguard Total Bond Market Index Fund Admiral Shares (VBTLX)
Vanguard Total International Stock Index Fund Admiral Shares (VTIAX)
Vanguard Total International Bond Index Fund Admiral Shares (VTABX)
Vanguard REIT Index Fund Admiral Shares (VGSLX)
Rental Properties
Starting his own business, with an amount he's willing to risk (this could be buying a corvette and renting it out on turo, he would still get to use it when he isn't renting it out)
then take up to 4% out per year(or an average of 4%)
If it were me, I would do a combination of start my own business with $200,000($75,000 of that going into an emergency fund for the business), build 2 or 3 rental houses or duplexes for $150,000-$250,000 each, add $15,000 to my personal emergency fund for the rental houses, and put the rest into VTSAX.