This is an analogy with real life, as you have made it to the 'big time' and don't need to worry about money anymore.
In most cases, you'll have more cash than you know what to do with! -
Even if you spend it all, you'll get loads more when you next pass a yellow 'Cashflow Day' square.
Things do get more interesting in the 202 game though. Now if somebody lands on your business, they can buy it from you and you lose the business and the cashflow. So there will be a downside to your game.
Also, you can franchise your business if you land on it more than once, getting even more cashflow income. However, if another player wants to buy your franchise, they need a lot of money to do this, so in the 101 game, cash is plentiful on the Fast Track, but it is quickly spent in the 202 Fast Track game.