>>35797964No. Especially if you imagine yourself as a real person in their world. Yes, it's basically a useless fish, but it's cheap and you don't have to catch it. Plus there are no running water sources near Pewter City, meaning you'd have to go through Mt. Moon, Viridian Forest, or Diglett Cave to even get one.
It'd take time to raise it without being a full time trainer, but eventually you'd have a powerful water type that would stomp Brock. Take a trip through Mt. Moon and you could probably work in Cerulean Gym even, and eventually start dating Misty.
That salesman gave you power, a job, and a future for 500 pokeyen.