[Ham]

In the Left View Window Select the menu : "Ortho"
Set the Background image to your vehicle.
Create a cube.
From that cube Extrude surfaces, and move vertices until you have roughly approximated the body contour of the vehicle in that view.

Thats the simplest way to do it.
Then use bools to cutout windows.

Then spend time on individual details like the tires and texture and it will come together.