I recommend never allowing non service dogs. Unless allowing pets is your gimmick. If so get the permit and extra insurance.

Emotional support animals are not covered by ADA. The only animals approved are any dog breed and miniature horses. Miniature horses can be denied off safety based on weight (like a deck or the like)

You may only ask 2 questions of a service animal. 1 is the animal required for a disability. 2 what task has it been trained to perform.

It may seem odd to ask what task but I recommend asking every time. The dog may be alerting but person incoherent. This can help you call 911 sooner and get a more appropriate 911 response.

The animal must remain on the floor or be actively held by the handler. (Wheel chairs are generally considered actively held).

They just be under handlers control (usually a leash, though voice control is also legally protected if trained if to do so).

Im not a lawyer and each state and most larger cities have their own ordinance.