@Too much.
The need for a co-pilot in the C208 is the same reason there is a need for a Co-pilot in a B1900.
Both are single pilot aircraft.
My company routinely flies two of our caravans single pilot as they are only cert'd for 9 pax (Which, I believe is the case for all of Susi's caravans. Which makes me wonder why they seat 12 but I stand to be corrected on that.)
For our other caravans which are cert'd for 12, it must be 2 crew.