The three main classes of assistance dogs are guide dogs for the visually impaired, hearing dogs for the hearing impaired, and service dogs for those with physical or mental / cognitive limitations. (breeders.net)
They then enter an intensive 6 month program to teach them the specific skills of being a guide dog. (samthedogtrainer.com)
Being a guide dog puppy walker is a very important and useful job! (pethelpful.com)