I have a Service Dog for my disabilities, and no, I cannot work. In Canada, a prescription from one's physician or nurse is necessary to support having a SD; in the States, it is important to get a script as backup, for proving your dogs are Service Dogs, as opposed to Emotional Support Dogs.
It is also a good idea to have your dog tested by a dog trainer, for public access; the Delta Society has some excellent guidelines. Then, should you have serious problems, you have a record of behaviour for your dog, but it is not necessary.
Service Dog protocol is important, and it is the people that do not follow it that cause problems for other SD handlers.
It is not necessary, legally to 'register' your dogs with SARA or any other program; SARA accepts any animal, provided one sends them the right amount of money, and has no official status whatsoever. Basically, it is someone's idea of an income for nothing, and will do no good should you need help from an outside source. Before taking your dogs in public as Service Dogs, it would be a good idea to check out such websites as
www.psychdogs.org Here, you can learn just about everything you need to know about PSDs.