So, do you usually start with a juvenile raptor and keep it for a couple of years before letting it go; or do you keep it for the rest of its life like a sort of pet? I suppose pet is the wrong word... From my very limited experience watching demonstrations, the birds appear to obey commands quickly but don't seem very tame beyond that.
As an apprentice you must start with a wild yearling (passage) red tail hawk or a kestrel (sparrowhawk) of any age. Apprentices usually go with the red tail (bigger and easier to care for). As an apprentice you can only have one bird at a time. Depending on your sponsor, you might release it after the first season and catch another for your second year, or keep that one for both years.
Once you can become a general falconer, you can now own two raptors. Many. choose to keep their apprentice hawk (it's like your starter in Pokemon, he's just a staple) and get one more. A general falconer can get nestling (eyas) raptors either from the nest or from a breeder. Others who are more interested in rehab type things might catch a raptor, teach it to become an effective hunter over a season and then release it each year. That raptor now has a much higher chance of survival.
And you are right about them not being pets. They do not need you, however, they trust you to provide for them and do sulk when you are mean to them. They are more like a hunting companion than a pet. However, they will get attached to you over time. For example, some falconers have released their red tail thirty miles away from their house, only to find it waiting for them in their backyard by the time they get back home.