Adopting an Older Sheltie                      
Hopefully this information will give you some insight on how to ease the older  Sheltie's adjustment into your home.          
When you first bring your Sheltie  home you may find the temperament is not quite the same as what it was at the previous home. This is to be expected as the dog is not only in new surroundings but there is much confusion in the dog's mind as to why he is here at all. The best advice that I can give is to be very gentle so that you will instil a feeling of security and calmness. If the dog was used to sitting in laps try to get them onto your lap and pet them a lot. House training. You are probably going to find that the Sheltie is going to have a few accidents for the first few days. This is also normal because your routines will be unfamiliar to them. Make sure that you DO NOT get too upset at the Sheltie for this because if you do it will be that much harder to form a bond between the two of you. When you take your new Sheltie outdoors, whether it is for him to relieve himself or it is to play, DO NOT let him run loose, unless you are in a fenced yard. Continue to do this; for about six months. I cannot stress this enough! You would be surprised how often it is ignored after a week or so at the new home. When you took your new Sheltie from their previous owner you created a sense of confusion in the Sheltie's mind because he ishinking "What did I do wrong? Where is my owner and when is he coming to get me?" Once he realizes that the old owner is not coming back to get them, there is a very strong possibility he will attempt to run away and try and find his previous owner on his own. What you have to do is keep him under your control at all times until the old bond is broken and a new bond is formed.  This does not happen overnight. This may sound like a lot of hog wash but believe me it happens more often than you would imagine. We have placed a few Shelties over the years and we have had three Shelties that have run within the first month of going to their new home. In every case the Sheltie was eventually caught while heading back towards our place. How do you know when a new bond has been formed? This is a good question and the only thing I can say is that when your Sheltie consistently comes to you when you call him, and he has his tail waging, then you are well on your way to creating a strong bond. Changing names. Sometimes you may wish to change his name. I would not advise this right away because this will only add one more stressful item for the Sheltie to overcome. Once the Sheltie has adapted to his new surroundings you can begin to change his name by doing the following. Start saying the old name followed by the new name every time you want him to do something. This way he will get used to the way the new combination sounds. After about a week, start to drop the old name, every so often, but continue to use the new name. Give him lots of praise when he responds to the new name but don't scold if he doesn't respond. Instead go back to the first step. If the above seems to be working okay then drop the old name altogether. Remember that this is not any overnight thing that you can do. It takes time and patience. Although there are not a lot of suggestions above I feel that they are important for you to try so that your Sheltie's adjustment  into the new household is as smooth as possible. 
Canadian Shetland Sheepdog Association