A printable (using 1 sheet of paper, duplex) guide for selling cars at Los Santos Customs. You can also bookmark it, and use the bookmark widget on android to have easy access to it on your Android phone. Or, on iphone go to the doc in Safara, click the Share link (top right) and click “add to homepage”. (You can also link to the google doc directly from your homescreen – Google it).
This is the easiest way to make money in GTA online. As soon as the game loads up I recommend you find a car on the list (or go up to the golf course as good cars often spawn here), steal and sell the car at any Los Santos Customs shop. Around $9,000 for 5 minutes work is very good going. And, by the time you’ve finished playing it’s a whole new day (in-game time only, hopefully) so you can repeat the process before you quit playing.