The questions you brought up apply to service animals, as those animals are trained to perform a specific task or provide a service with guide dogs and seizure dogs likely being the most common. 

Examples are seeing eye dogs, diabetes dogs, dogs who can sense seizures, and the list goes on. 

.: a physical or mental impairment that substantiallylimits one or more major life activities).Major life activities includebut are not limited to:walking, seeing, hearing, speaking,breathing, thinking, communicating, learning, performing manual tasks and caring foroneself.Impairments that are considered a disability under the Fair Housing Act include suchdiseases and conditions as orthopedic, visual, auditory and speech; cerebral palsy,muscular dystrophy, multiple sclerosis, autism, seizure disorder, cancer, heart disease,diabetes, asthma, HIV, mental retardation, mental and emotional illness, drug addictionand alcoholism.

They could have one dog for depression and a second dog for alerting them to oncoming seizures.

It's the greatest property grab and asset seizure in human history. 

My husband has cystic fibrosis and seizures and is on a medication that's almost $300000 a year.

She tells me that her roommate is having seizures, that she's called 911, and that 10-12 of her roommate's friends are streaming out of the apartment as we speak.

Nothing really, but even though I am not allowed to question her disability I could ask her what specific service he performs, and I bet it's something related to seizure, hmmm something like that, cough cough.

They may be medical alert dogs that warn their owners of impending diabetic crises, seizures, etc.

ConstitutionFourth Amendment - Search and SeizureThe right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized.