When the company hires you they have to pay for your training. Because of the cost of training, and a few other factors, they require you to stay in your current aircraft for 2yrs as an FO, unless upgrading, that way they can get their money's worth. Has nothing to do with certificates. If they pay to train me in the 145 then I'm stuck as an FO in the 145 until upgrade or until my seatlock is up, whichever comes first.