first off, welcome.
Honestly, these dogs do require alot of 'family' interaction. If your planning on chaining them outside, not a good idea.
Growing up, years and years ago, my family had always had dogs. One was a gsd that was chained up outside to a dog house. He was a nervous mess, I was a small kid , what did I know? I think being chained up outside, made him not only a nervous mess, but anti social , and well he'd nail anyone that walked past him. He also had separation anxiety. Just not a good thing at all.
if He's familiar with your janitor most likely not a problem.
3. Yes, and who knows , these dog can be territorial, especially if they are living outside most of the time, it could be a liability but also depends on the dog.
Depending on the dog would depend on whether it would be protect anyone, they are usually more about protecting themselves than others.
A bark is a good deterrent but you can't expect a dog to go after a burglar especially if the dog is living outside.
So, my vote is honestly, I would not get a gsd if I were you
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