Unlike in the video games, players will not earn an amount of money for defeating any other trainer. In fact, sometimes it will cost the player to even challenge a gym! Earning money in the game will entirely depend on the players. There will be opportunities to earn money throughout the campaign, based somewhat in the story; however, the primary way to earn money is to simply make an effort to earn it. Go out there and look for work! Heck, you can even bet on pokemon matches if you can find another trainer willing to take a risk.