You don't need the money glitch. Play the game with the least powerful cars you can compete with, meaning maybe a couple of attempts to win, meaning more prize money. If you don't want to do that then just grind by doing everything available, including seasonal events. I did the 20,000,000 credit glitch once. I never spent the credits, or did as others did by spending the money on certain cars and using my garage as a bank, millions of credits stored as cars ready to sell.
I regretted doing the glitch, which is why I did not spend them. I currently have 30 million credits (20,000,000 cheat credits/10,000,000 honest credits). I only buy cars when I know I will have a bank balance of 30 million credits remaining, if no glitch then that would be a healthy 10 million credits banked. And I purchased Ferrari FXX, Bugatti Veyron, RUFs, McLaren F1/F1 GTR/MP4 ect. And I wasted credits on silly cars to mess with.
I have not completed career mode yet, still S and most of International A to do, the latest RedBull events still to do, so more credits will come. And I have hardly raced online yet providing yet more credits.
Plenty of in game credits are available.