Many "money generators" require you to download software or provide login info, which are common methods for spreading malware or stealing accounts.
Focus on hitting "Perfect Starts" and "Perfect Shifts." Each one adds a cash bonus to your race total.
The CSR Racing 1 money glitch is a notorious exploit that has been a thorn in the side of NaturalMotion and the game's community. While exploiting glitches can provide a temporary advantage, the risks associated with using such glitches far outweigh any benefits.