It's more likely the bookstore would be the loss-leader for the cafe.
The usual killer, as you've identified, isn't people sitting at the tables but the rents. Possibly you could do a quite "successful" cafe as a non-profit that owns the building it is sitting in.
The usual killer, as you've identified, isn't people sitting at the tables but the rents. Possibly you could do a quite "successful" cafe as a non-profit that owns the building it is sitting in.