This. I've been reading up on ESAs, too, and saw a tip that said most places won't ask your dog to leave unless it is causing a problem, so good training (like Canine Good Citizen as another poster mentioned) is probably the most important part. I have a note from my doctor (PTSD is a bitch) and that was all my apartment building needed to allow my dog (their policy was no pets but they honored the letter).
"The Americans with Disabilities Act allows you to ask someone with a service animal only two questions: Is the animal required because of a disability? What work or task has the animal been trained to perform? Specific questions about a person’s disability are off limits, and, as I mentioned, people are baffled by the distinction between service animals and emotional-support animals."
This 2014 New Yorker article made me furious, so here are some relevant points
"Contrary to what many business managers think, having an emotional-support card merely means that one’s pet is registered in a database of animals whose owners have paid anywhere from seventy to two hundred dollars to one of several organizations, none of which are recognized by the government. (You could register a Beanie Baby, as long as you send a check.) Even with a card, it is against the law and a violation of the city’s health code to take an animal into a restaurant. Nor does an emotional-support card entitle you to bring your pet into a hotel, store, taxi, train, or park.
"No such restrictions apply to service dogs, which, like Secret Service agents and Betty White, are allowed to go anywhere. In contrast to an emotional-support animal (E.S.A.), a service dog is trained to perform specific tasks, such as pulling a wheelchair and responding to seizures. The I.R.S. classifies these dogs as a deductible medical expense, whereas an emotional-support animal is more like a blankie. An E.S.A. is defined by the government as an untrained companion of any species that provides solace to someone with a disability, such as anxiety or depression. The rights of anyone who has such an animal are laid out in two laws. The Fair Housing Act says that you and your E.S.A. can live in housing that prohibits pets. The Air Carrier Access Act entitles you to fly with your E.S.A. at no extra charge, although airlines typically require the animal to stay on your lap or under the seat—this rules out emotional-support rhinoceroses. Both acts stipulate that you must have a corroborating letter from a health professional."
Okay, no more Internet for me tonight. That article made me sick. But I hope the info on the two laws helps.