I've had a cat classified as an ESA for about seven years now. My partner has some legitimate anxiety issues and we were given an official notice from a therapist and a second one from a medical doctor that we need to renew every few years. Funny enough we actually only had him classified as an ESA at the suggestion of a leasing agent in the first place to avoid pet rent which has been awesome. We've avoided all pet deposits, extra pet rent, and have had him in "no pets allowed" apartments. Honestly, in the beginning it was as simple as asking our primary doctor for it outright and they wrote a hilariously simple - "I'm a doctor and I recommend this person have an animal" letter. It was genuinely one sentence.

I have also lived in 4 different states in managed apartment complexes during this period. Some complexes have not given even the slightest fuck and some have called our doctors to verify the legitimacy of the paperwork (HIPPA is a thing and they get told to fuck off if they do😂). It's all going to depend where you're trying to move to and the type of place. In every case we've let the agents know we have an ESA classified animal at lease signing and submitted whatever they've requested.