Most people are saying you can only do it with a bike but here's more info

Forums/t=5725169/motorcycle-glitc...t-tut.html

Thanks dude will try this.

The way i did it today.--

Go to Invite only session

Steal a nice car that you are able to sell(hummers or range rovers are the best)

Upgrade it as much as you can. Spend over 200k on it.

Buy the insurance

go to sell, press sell and as soon as you sell it press |start, Left on the D-Pad, A,A| It will bring you to the ingame market place. Wait 5 seconds and press B

Once back in LS Customs you should be in the car.

Wait about 15 seconds and repeat again.

If done correct you'll make 2m easily in 20-30 min.

EDIT--

I used a range rover and upgraded it to the max. I got 48k for it everytime ALSO, DO NOT BUY THE IGNITION BOMB!

Thanks going to try this it keeps spawning me outside and saying not takind vehicles. But will try that.

PENGUIN9NER wrote Thanks going to try this it keeps spawning me outside and saying not takind vehicles. But will try that.

Don't do what the first guy said. That version is only for bikes which will only give you about 18-25k. When you get back into LS customs after pressing B from the in game store. You'll notice a small yellow loading circle. YOU MUST WAIT FOR THAT TO GO AWAY!