The caveat being that the pokemon can't just do the job for you. People still need to put food on the table.

I work as a grocery store cart attendant, so you'd think I'd go with Machoke or Gurdurr, but they could basically do the job themselves, so instead I was thinking of Carkol: you could attach a harness to it and it could push the carts just like one of them fancy remote control cart pusher machines.

I was thinking Whirlipede, but its tendency to break loose and steamroll anything in its path wouldn't be great in a busy parking lot.