This is a discussion and decision that needs to be made by you, the airline, and your chief pilot.  The BE1900 can be a demanding aircraft and we do not recommend training as a captain if your role will be SIC.  Once a student is committed to PIC training, an SIC type rating will not be rewarded as a second place to a candidate who does not perform to the level of captain, therefore the decision to train as PIC should not be taken lightly.