Wild take is mostly only for juvenile raptors (only exceptions are Kestrels and Great Horned Owls as they are almost impossible to determine their age by plumage). There is a fledgling season where a chick can be taken from a nest, and a normal season where the bird is trapped while it's on its own.
A fledgling will be imprinted onto humans and cannot be released back into the wild ever. It is way too accustomed to people and can be a nuisance at best and a danger at worst to the public if released.
A wild trapped juvenile is a normal bird that is trained to hunt cooperatively. They can be released at any time or kept their entire 20+ year life.
Wild birds can not be sold, but they can be transferred to other licensed individuals. Any tit for tat stuff can lead to trouble with this.
If wild raptors are kept for a certain number of years, they can be bred and their offspring sold to other falconers or licensed individuals. These captive bred birds cannot be released into the wild but they in turn can be bred too. They have a seamless band put on their legs when they are chicks to differentiate them from wild birds.
Importing birds from other countries is extremely expensive because as far as I know they need to stay in government quarantine for 30 days or so.
My 3 Harris Hawks, all captive bred. Their native range is the American Southwest and Mexico but mine are from Seattle, Los Vegas, and Baton Rouge: https://falconry.party/post/13676