You don't need to earn a million dollars per year to be a millionaire. The president gets a salary of $400k per year and has literally all of their expenses paid for, including room, board, maid service, butlers, cars, airfare, clothing, medical care, etc. They serve for 4-8 years, and they receive compensation for life. It doesn't take long to become a millionaire in that scenario. There are no US presidents that aren't millionaires.