Number of hirelings: Starting at level 1, you can employ 1 + ( 1/2 your level rounded down) + PER bonus (negative PER bonuses count against you) hirelings.
ex. a 3rd level fighter with an 8 PER can have 1 hireling (1 + (3/2 rounded down to 1) -1 PER bonus)
Morale: A hireling must roll their morale or better to avoid fleeing when faced with danger (including combat). An exception is made for meatshields, who only make their morale checks when the first person dies and again when and if 25% of their number are killed. The morale roll is affected by the PER bonus of their employer