Reckless Racing Ultimate

Another easy achievement all you need to do is click the car icon top right of the screen or press X if using the controller, click on buy car or scroll down with controller then select the category of car you would like I selected the "cavodi carabelle" under "street/dirt" which was $6000 in game credits. (I think this is the cheapest one but can't remember)
Double click the vehicle and you've now bought it or just select and press A if using the controller.

Enjoy