I wouldn't worry too much about the title of a rescue dog. When we adopted Norman, we was from a group of 75 dogs up here from North Carolina. I would say that 90% of the dogs were under four months old, and there were next to none more than a year old. If you rescue a puppy, you really shouldn't have to worry about behavioral issues. If there are any, the dog is still plenty young to discipline easily.
As far as bad experiences go... When I was younger, maybe 10 or 11, my grandma and grandpa adopted a dog that looked similar to the dog from My Dog Skip. It was a great dog. It was quiet, loved kids, and it obeyed orders relatively well. However, the dog had more energy that they knew what to do with. It was hyper as all hell and spent the whole day bouncing off walls. My grandpa had medical complications (I was too young to really know/remember what they were) which lead to him having a tube coming out of his stomach to allow stuff to drain out. One day the dog jumped on him while he was asleep on the couch and literally ripped that tube out him. They gave the dog away and adopted a Yorkie. Much easier to manage. I wouldn't let that story deter you though. Part of the problem in that scenario was they had a dog that probably needed a good three miles of walking a day, and between being old and taking care of my grandpa, my grandma could only manage a lap around her neighborhood a day. Some dog breeds need to be tired out or they behave like that. Norman (my dog) is kind of like that. Luckily, he'll obey orders to chill out if we give them, but if we don't his energy level always seems to be a 100%. Even after a five mile walk, he barely seems phased.