its up to him in the end. if you wanna do cardio post workout then go ahead, if it works for you. if your goal is more to burn fat than to build muscle, i would try more interval training and aerobic workouts. otherwise, i think doing a balanced split of cardio in the morning and weight training later in the day is your best bet for trimming down and adding muscle mass at the same time.
i work out on a five day split....workouts generally an hr long... and i personally feel that i have no more positive energy to spend on cardio after my lifts.