Well, this can be done in several ways. Short of drawing the cars in Ps, you could convert images to have a "cartoon effect".
Here is on of many VIDEO TUTORIALS that shows some basic techniques for converting photos. The creator gets a bit carried away in the end but it will give you an idea of where to start. This is all assuming that you don't already have the cartooned photos of the cars. Also search YT for other videos about cartooning photos in Ps.
The next step would be to arrange them in a suitable composite. This is not that difficult as it's just a matter of importing the individual (cartooned) images into a single document, using free transform to size and arrange. The biggest headache I can see is making sure all the cars are in the same perspective plane.