housetraining a German Shepard puppy?

If you doubt your ability to catch him in the act, and scoop him up and outside in time to finish, then consider finding a puppy raiser to do the first six months or so. Check with local youth organizations such as scouts or 4H. Odds are good you'll find some help there.

The problem with doing an inadequate job of house training (allowing some accidents to happen) is that the dog never fully develops the kind of strong desire not to toilet inside that you need for a service dog. Each accident that occurs uninterrupted sets back toilet training a month or more because toileting in and of itself is reinforcing. To be blunt: it feels good to empty one's bladder or bowels, and that feeling encourages the dog to do it again. We need that reward history built up in the appropriate potty locations, not the inappropriate ones.

—edit—

Crate training is also my preferred method for toilet training. However, one cannot keep a puppy in a crate all the time. It would not only be terribly cruel, it would not teach the dog to be loose in the house without toileting. That aspect of toilet training can only be taught by having supervised access to the house where he is prevented by the trainer from toileting indoors. When he is out of the crate and supervised, the trainer needs to be able to recognize when he is about to go and hustle him outside to do his business or at least to finish his business. If you can do that: GREAT. Go for it. But if you think you will have trouble getting him outside in time, your only options are an inadequately toilet trained dog or a puppy raiser.