The service dog

Having a therapy dog has changed my life. There are 2 kinds of working dogs: Therapy and working dog. The working dog is trained to do a host of services. Help the blind, people in wheelchairs, etc. 
The therapy dog is an RX dog prescribed by your doctor. When I flew to Florida all I needed were the letter of prescription and his updated health records. My therapy dog is named Oliver. He is well trained and helps me feel safe if I fall and when I go places alone. 
Oliver is a chiuaua. He was given to me as a puppy and I have trained him for this since. I get many comments on him because he is very pretty (fawn) and small. Most people do not know you can use small dogs as service dogs.
Before My diagnosis, I volunteered for the animal rescue league in Denver. I have 2 cats in the house and at the time there were 3. Since my roomie had the 2 cats and I had 1, she wanted no more animals, so I volunteered for the dog behavioral department. 
I started out walking dogs. Then I could not handle the big dogs, so I would only walk the little ones. I was exhausted after 2 hours, I did not know why at the time. I then took a break and have not gone back since my diagnosis. 
I learned that I never would have been able to handle a large dog as a service dog. Sometimes Oliver wears me out as he is still a dog and still does dog things. Not often, but he can get tired and I have to carry him. Then I can only do it ten minutes at a time. 
I have severe anxiety as well, and he helps tremendously with that. He also helps keep me busy. After all, he is 1.5 years old now and very active. My room mate loves and adores him and plays with him often. She feels sometimes I neglect him, but unfortunately, I get fatigued and can't play with him. He is well fed, has dog insurance with the vet and I train him constantly. She does not train, feed or walk him, but I am so grateful she plays with him!
This also keeps he and I in a "master-servant" relationship. When he sees her, he gets excited whereas when he sees me he is on guard. He knows I am the stern trainer and she is the fun, playmate. My concern is that he would want to play at a time when I needed him most, such as if I fall. 
Because he is certified he can go anywhere with me. I have to stave people off as he is little and cute, and some never ask if they can pet him. But the fact that he is a chiuaua and a service dog just makes them so curious and respectful of him. Imagine, seeing chiuaua's in this different light? Not the yappy, nippy dogs they are claimed to be? Oliver is not that kind of dog. He growls sometimes and barks, but it is rare, and I nip it in the but right there. 
Also, as he is so small, I had to make him a vest. I did costume design when I was in my 20's. Then I ordered the patches from sitstay.com, sewed them on, and when I put the vest on, he knows it is time to work. 
There are other ways to get service dogs - you can go through a service dog specialty center which could be thousands or train your own dog with certified professional trainer. For a therapy dog they must have enough training to understand and obey your commands and not use the bathroom while inside buildings. I use public transportation a lot and walk Oliver when we are outside and, of course, bring bags and treats (bully bones keep them busy for a long time). 
Whatever dog you choose or wherever you chose to train it be sure it is a dog you can handle. I am fully ambulatory and can walk a dog, but my limbs are week, so I needed a smaller dog. He is perfect for me. He also lives longer than any other breed; up to 30 years! So do your research, leave any outside information and myths you have heard about any breed and do what works for you!
Good luck and happy dog hunting!