Re: Bad back in need of help.
Is he overweight? What is the cause of his back pain?
I would say just about any bodyweight exercise would be good for him i.e. - air squats, push ups, pull ups, sit ups, lunges, running, swimming, and whatever else you can think of. Once he has built up some muscular strength and hopefully alleviated his back pain you can introduce him to resistance training i.e. - back, front, and overhead squats, deadlifts, presses, weighted pull ups, et al.