Pros
If you are a young and into cars, it could be a great first job. This was my first job in high school and loved it. It taught me how to drive, park a car, and many others. Did everything from washing cars, painting, and pulling weeds.
*Will keep you in great physical shape*
Cons
Can get very hot in summer time getting in and out of cars that have been baking in the sun all day. On "lawn days" where we would have to move cars off the grass so the mowers could mow the grass, I clocked in 21 miles on my fitbit from walking around for 12 hours moving cars.
Hours can be long and pay can be low. A porter is pretty much the grunt of the dealership.