Mine has rust bubbles on rear driver side quarter panel, just above plastic bodykit and a wee bit where the rear bumper meets the same quarter panel.
Also on both sills where the front wings meet the sill. You need to open up the front doors as wide as they'll go and check the little square area on the sill and behind the very bottom edge of the front wings.
Make sure you view any cars when they are dry and not covered in beads of water. Also make sure the car is clean as well.