If the dog will be living primarily on its own outside the house I would highly recommend looking for a breed other than a GSD. GSDs bond strongly with their families and really want to be close to their people as much as possible. They also need lots of exercise and need to be engaged and interacted with in their physical and mental exercise ... they are not the type of dog that will play on their own and tire themselves out. Left alone in a yard, no matter how nice or big, they will get bored and will then potentially get destructive or disruptive (i.e. barking at everything that moves, or walks by, digging up the yard, tunneling under the fence, etc.).
The barking at passers-by and such can be addressed with proper training, but without a sufficient amount of exercise (both physical and mental) every day, I don't know that even training will help. A bored GSD is going to find a way to alleviate it's boredom. They are extremely smart dogs, and as such need to be stimulated in positive and engaging ways every day or they can and will be a tough dog to live with regardless of whether they live in the house or outside.