The only successful model of a bird daycare I can think of is one that's done by vets:
https://www.facebook.com/pages/Currumbin-Valley-Birds-Reptiles-Exotics-Vet/141797059204766
I think if you were a board certified Avian vet, then it would be a great idea. But without knowledge of how to manage virulent disease, health complications that may arise, it would be rather hard and I'm not sure anyone would want to go to the vet to pay for a recent certificate of health to drop them off for daycare every time, considering they would also be paying a fee to keep the bird there.
Perhaps if you collaborated with an avian veterinarian interested in coming in once or twice a week to have your clients checked over before agreeing to accept them into the daycare, or an agreement with a vet clinic to send your clients there it would work.
What I would be considering if I was you would be these things:
- how many clients am I expecting? Out of how many of those clients will be small, medium, large, or XL birds?
- will I have staff to clean, to train, to socialize, feed, and manage the store front?
- can I form an agreement with a newspaper company, paper company, etc. to ensure I can change the cage lining daily, if not twice daily?
- will I be fitting the cages with full spectrum lighting, or will I have an outdoor space with enough room for flying for flighted birds or climbing for clipped birds?
- will I have an area to bathe birds in the way that their owner knows they like best?
- will my store be located in an area where I won't receive sound complaints from neighbours due to the screaming/talking of several birds housed together?
- can I form an agreement with toy companies to bring in clean toys? Especially considering that toys brought from houses may potentially be hazardous to other birds?
- will I have a room to separate dusty birds from oily birds? IE, will I have an appropriate ventilation system to prevent certain species, such as macaws, from developing or resurfacing sensitive respiratory issues?
- will I be keeping birds for the day, or for the week? How will this impact my costs upkeep?
- what will my liability clause be should an individual bring in an unhealthy bird that was deemed "healthy" by a vet? Will I require a blood test specifically to accept new clients, or just a general check up, or both?
The list is extensive and exhaustive. I recommend contacting a professional who runs a parrot sanctuary, rescue, or the veterinary clinic to see how feasible a parrot daycare would be and what they would suggest.