When setting out on the task of house breaking an older dog, you just have to remind yourself that the principles of house breaking a dog are the same, whether it is an older dog, or a new puppy.
The only problem you face is that, since he or she is an older adult dog, it must have received some sort of training, BUT, you do not know how well or how poorly the dog was initially housebroken and or trained.
Another unknown quantity about an older dog is the extent to which it has cultivated bad habits, if any. The more bad habits the dog has cultivated with its former owners, the more difficult the housebreaking and training process is going to be, but nevertheless, training an older dog has been done and can be done.
Rules, and family participation, take on extra importance with the training of an older dog.
The family would have to get together, this would involve every human who resides in the same household, and should also include regular visitors who spend a lot of time at the house.
Draw up the rules you want the dog to follow, get everyone to familiarize themselves with it, no ifs, and no buts. The dog gets the same treatment from everyone.
Once the rules have been agreed upon, it is imperative that everyone remembers them and follows them so as to be consistent and not confuse the dog in any way, which will make for speedier housebreaking of an older dog.
The next important rule to be followed with housebreaking an older dog is 100% supervision. This supervision has to be there, till the humans learn all about the dog and the dog learns all about the humans in the house.
Remember you are dealing with a dog that has lived with humans before, he or she may have been spoilt and over indulged in, or may have been ill treated and abused.
You the new owner will never know, till you find out, and the only way you are going to find out is by observing the behavior and disposition of the dog under all circumstances and situations.
The only way to observe all of that would be to have him or her within sight 24/7.
You cannot always be where the dog is, but the dog can always be where the humans are, so with this in mind, the areas of the house to which the dog is permitted has to be restricted, to permit the 100 percent observation as entailed above.
So, feel free to adopt an older dog. There are a lot of adult dogs that have been abandoned and rescued and are in need of good homes.
Spend the extra time and the little extra effort to learn about the dog, by implementing the above, then go about housebreaking and training him or her just as you would train a new puppy, it should not be different after that.
Here's to having fun while housebreaking an older dog.