Proof that money doesn't necessarily breed greed: In their 2015 Annual Letter, Bill and Melinda Gates explain their smart and simple vision for a healthier, happier world. These two have been leading the charge to cure people in poor countries of illnesses erased from wealthy countries last Century. Now, they want to heal us all by suggesting everyone join the effort.
Studies show that service to others is a powerful immune boosting activity, and even confers longevity: though recent research suggests such health benefits only come when one is motivated by true concern for others and not a desire to benefit the self.
With a long, strong track record of service, it's safe to say the Gates duo will likely reap the health benefits of volunteering while improving the health of tens of millions of their fellow global citizens. Not bad for a second career!