you mean a "Class Rating" .
is the aircraft you want to fly under 4900Kg? I think the ceassa 208 is but it is best to check.
I guess you have got a JAA CPL single engine rating as it is only single crew i think.
you will be the commander/ Captain?
I just think its 6 hours of flight time (around that amount in a cessa 208) and a test to get a SET rating Single Engine Turoprop rating.
if you want to make money from flying this then read EU OPS 1.960.
You cannot fly single man crew without 500hours or an IR rating with the company having an AOC. If the company is taking money from people apart from training flights without an AOC Licence then it is Legal.