The best thing you can do with that money is invest in bitcoins and hold those coins for a long term without investing it anywhere as investment involves risk and you cannot afford to risk this high amount as holding will give you guaranteed returns in future when you will sell at higher price.
There are many things better than only keep money like example trade with altcoins,but if he decide to trade with 500,000$ I dont suggest that I just suggest to deposit maybe 10-20$ and each trade use 1$ for trading because bust risk is lower and you can make test your skills for longer and then if he got some trading skills depo some bigger amount depends how much he want make money.If he want millions per year to make I suggest 50.000$ to use for altcoin trading if he get skills but if he not get then to keep alll half million $ on btc wallet.