This is cumulative so you don't need to worry about saving your money. If you're going for the completion you'll definitely earn this before finishing everything else. After completing the story and Mission Mode challenges I had about 150k sitting in the bank (Keep in mind I would still have needed to grind local matches and player levels at that point).
Best way to earn money is via Online matches (1000 coins for an A rank win and 1500 for an S rank win), I ended up with around 50k after trading wins for the online related achievements.
Story and Mission mode fights give 300 coins per win (Mission mode also gives you a bonus based off what score you got after you complete the map, 1000 for an A rank overall and 1500 for an S rank). Local matches give you 200 coins per win.