During Campaign Mode, you receive money following each win based on all the big plays you make during the game, as well as the bet you make at the outset. At the outset, you can only bet $10-15k, but by the end of Division 1, you can bet $35-40k... whether you win or not is determined by the point spread, and if you beat the spread or not.
The breakdown on dollars per big play goes like this:
Clash Moves - $2k
Unleashed Moves - $5k
Dirty Hits - $3k
Injuries Caused - $7k
Turnovers Forced - $5k
Touchdowns Scored $12k
So, in order to reach $400k total, you'll probably need to win the point spread Max Bet (70k) and have a whole lot of big plays... something like 30 Clash Moves ($60k), 10 Unleashed Moves ($50k), 10 Injuries Caused ($70k), 4 Turnovers Forced ($20k), 8 Touchdowns Scored ($96k)... all that adds up to $366k. All this needs to happen in eight minutes of game time (2 min quarters), so stop the clock every chance you get!