Hello and welcome to yt!!
A few years ago I saw two yorkies that were in fact service dogs. They do great because they are so loveable and in tune with you and your feelings. If you really want one as a service dog I would pick out a puppy and have someone train it for a year. If you could I would look into programs that train service dogs for you. Usually a family will get a puppy and train it for you and give it to you fully trained in about a year. If you wanted to train it all on your own I would say you would be better off getting a older yorkie. This would be alot less stress on you and you woulden't have to deal with all the puppy stages. One of the most important things is that you need to look closely at the temperment and disposition, you want one that is mellow and laid back rather than hyper and bouncing off walls. All in all, it is a great idea and yorkie would be perfect. Good luck to whatever you decide!!!
