What money making method do you use? Is it effective?

[DVN]

Buying and reselling items is popular, as Marvin said above and can make you the fastest chunks of profit ranging from $10,000 to $30,000 depending on the vehicle etc.

Earned 2 million in 2 weeks <3

I need to try that, are all cars good? I only have about 150k.Also generally I never get any trades when selling.

Well, there is always demand for vehicles no matter how 'bad' they are. You just need to find the right buyer and set the right price. Some people are more desperate for a vehicle than others for various reasons you just have to pick them around a bit and see how they react, also the better the car price as standard the more profit you are set out to make.