Work will be irregular, regardless of "full-time" or part-time. The days are not structured. This workplace is geared towards kids, not mature teens or students looking for a serious pay.
There is no real application process, anyone can land the job. The red flag is that the owner takes a sketchy picture of you. The owner has absolutely no organizational or managerial skills. You won't know what you're doing, where you're going, or when you'll be working until the day of. Sometimes, you won't even get any solid details.