Since you're going to be moving down to Canada D4, I wouldn't keep/buy a single player on your roster with more than a $7-8000 salary. You should be able to promote easily with a low payroll just by managing gameshape and you'll increase your weekly profits that way.
But either way, wait until you see what division you're relegated into before you start shaping your roster. You might be in with 14-15 bots.