So....you're only working 6 days a year?

I don't see it working, at least on game days anyway, just too much going on, plus you'd spend half of your time in traffic

Or... you pay your own parking... and detail the car in the parking lot... at the game... and hustle getting it done in 4 hours.

Double that. Plus you need a compatable vehicle. Game day only isn't a good idea since you'd be marketing to outside the area clients. Don't worry about competing with shops -- mobile detailing IS a very viable business option but just do it where you are when you can and market to the people in your area.

The thing is, you need some experience here. You need to know the difference between what a car owner who thinks a clean car is and what a professional knows a clean AND protected car is inside and out. You need to know what soaps to use, how to apply them, how not to scratch the various materials on the car, how to apply the various products you use, as well as what products to use. Thinking you can just go to Autozone or even get online and grab a bunch of stuff and use it CAN be a huge mistake.

I don't want to discourage you but I'd recommend you go work for a car wash and see all the things they're doing wrong -- THAT will teach you what you need to be doing. Do that for the next 6 months, get some experience detailing friends and family vehicles for free or low cost and then branch out on your own with business cards and advertising. By then maybe you'll have a spare truck or minivan and you can pull up and look professional. While you CAN do this out of your personal vehicle, it will be difficult and likely lose you business in the long run.

Do they still do the shuttle from the mall to the stadium? You could set up at the mall parking lot, try to catch a few customers as they come in, have them park in an open spot (open spaces around, and knock it out while they're gone. That way you wouldn't need to worry about transporting them.

My youth minister in high school had a mobile trailer rig like that for a side job. My buddy and I worked for him some, and then my buddy built his own rig. He ran that thing all through college, then trained and sold it to a younger kid when he graduated. Can definitely make good money at it. I don't think game day is a bad idea, but don't limit yourself to those days. Plenty of business around. We would mostly go to people's work places. Most of the appeal to the car owner is the convenience of not taking their time taking it somewhere.