I do this every 48 mins,(1 gta day) and my car gets $97,000 each time, the more you spend on your car the better, this method is still unpatched even with today's update, but hurry, they will patch this soon
Edit: Just sold my car over 100 times, i made 6 million, so if done right, you can keep selling and not wait for a new day on gta























