When I was 15 in Tennessee (it's been a while) I cut grass, washed windows, cleaned out garages(got lots of neat stuff given to me) and even painted some. Now a days try the clean out garages and basements. Many people will pay you plus give you the junk. Lots of junk sells on ebay and craigslist now.

Try the supermarkets, or fast food places.

In the state of Tennessee, the working age for a minor starts at 14.

Probably at Walbaums as a Cashier