When I lived in the Schumaker area the places that I frequented the most on Parsons were the Ace Hardware, Planks, IGA, Library and Schottensteins which has since closed. Had the Subway been around I would have gone often. I think it depends where on Parsons you intend to buy. The block closest to Livingston could draw traffic from the Hospital development and employees. Also, if you intend to draw pedestrian traffic think about what side the street may work best for you.
The closest coffee is on Third at 'bucks or Mojoe so a coffee shop near Liv & Parsons would probably draw from the Schumaker area and the Hospital. Could be a winner.