Hi. I'm Jeanne. I had an australian shepherd until I got divorced. He is the BEST dog - Aussies are now one of my all-time favorite breeds.
I think it's great you are looking at an older dog. As a long-time rescuer I always suggest people with children, especially young children adopt an older dog and NOT a puppy because an adult dog has already settled into their personality and you don't know what a puppy's natural demeanor is going to turn out to be.
Anyway, Aussies can make great house pets, but you have to be dedicated to giving them at least an hour of vigorous exercise every day. My Aussie, Rocko, LOVES to play frisbee and he is very good at it. You have to force him to stop! So, we'd take him outside 2 or 3 times a day to play frisbee and when he came in he may want to play fetch inside, but was otherwise very obedient.
Aussies are very smart. Once he matured, he picked up new tricks very easily so I suspect you won't have a difficult time housebreaking him. I've always found, with rescue dogs, it's easier to housebreak adults than puppies.
I hope everything works out, but my one BIG word of advice is: don't adopt this dog if you don't think it's exactly what you want or need. An Aussie WILL try to herd your kids, cats, etc. They tend to be protective of their "herd" so may be wary of strangers, but they are awesome dogs if you can keep up with their energy-level!