Mandy -
I did adopt Buddy when he was 3 years old. His history is very vague as he was just dropped off at my veterinarian's office for "boarding" and no one ever came back to get him. The address, name and phone number were non-existent of the "owner". They did a police report as they thought maybe he was stolen/lost when they couldn't contact the owner, but after about 6 weeks no one claimed him. No leg band, no microchip.
I was working as a vet tech for the vet (she is a small animal avian vet) and had fostered several birds prior to Buddy (first a goffin cockatoo, then a galah, then a green cheek conure, and lastly before Buddy was a Umbrella) when she asked me if I would foster him. I at first fostered him when the office was unable to contact his "owner" but fell in love (as I always did, but finally decided after about 3 months that I needed to keep one for me for forever which was Buddy).
Buddy didn't know how to step up on arms or hands and was very hesitant at first. He had been touched though as he would love scratches and pets. He sat well on a free stand that was connected to his cage. His vocabulary was pretty developed when I got him.
He has a very mild timid personality still compared to the other cockatoos I fostered....new toys can be very scary as well as new people so just have to take everything slow with him. But he has done so well. Steps up now and gives lots of loves and loves to ride in cars and go to the vets. He is 11 years old now.