I'm doing my cousin John a favor. Anyway, To be more specific, I'm talking about the game in Goldenrod/Celadon City.
8 Levels in total
In each level, a certain amount of coins can be obtained. The higher the level, the more coins that can be obtained. Assuming the player does not quit, the interval is as follows: Level 1: 20-50 coins Level 2: 50-100 coins Level 3: 100-200 coins Level 4: 200-500 coins Level 5: 500-1000 coins Level 6-8: 1000+ coins
8 is the maximum and when you reach 250,000 you win and exits Source
There are 8 levels.
Source:http://bulbapedia.bulbagarden.net/wiki/Voltorb_Flip