In general, during a visit to the shelter only 1 to 5 percent of the dogs might qualify. Sometimes none will qualify. Service Dog organizations have to make regular visits to the shelters to occasionally find a good candidate. Fifty percent of the dogs selected will have hip displagia or other heath problems that will then disqualify them. A poor selection process may find a nice or cute dog but you should never shortchange your disabled client with a somewhat satisfactory dog.
Most dog trainers love dogs and training dogs.
This is only the beginning. If you have ever trained a novice class of individuals who have never trained a dog before you know that training dogs is the easy part. Training people to train their dog or maintain their dogs training is the hard part. Now add to this you have to train a person who is not as able to move with, motivate, correct, and in some cases understand your instructions right away. Training Service Dogs involves all of this plus the fact that your are making a ten year commitment to help this team whenever they needs it.