Yes, you can make money on Overwatch betting. You can find several sportsbooks that offer wagers for Overwatch tournaments. If you have any familiarity with the gameplay and players or teams, you can bet on different betting options like match winner, most kills, tournament winner, amongst others.
You need to provide your identification and proof of income to register on most reputed sportsbooks websites to register an account. The legal age for gambling can vary depending on the laws of where you live. Pretty much every sportsbook website will have a minimum age limit requirement of 18 years, if not 21.