Then he can't afford to live because he invested 100% of his monayz. But you're right, investing is definitely the best way to increase your money; but saving on the side is never a bad idea either. When I was still in college I lived with 3 dudes who were making more than I was since they were working full time, but their budgeting was literally "get paycheck, make paycheck last until next paycheck". If they had money left over by the next time they got paid, they went out and bought a ton of booze or w/e. They also complained about wealth inequality while doing this, lol.