IMO … Your a professional when you get paid to train horses or riders.
That said there are good trainers & bad trainers. Very experienced trainers & green trainers. That will forever be a mainstay. Just like there are good drivers & bad drivers.
Some trainers are better training horses ~ while some are better w/riders. Some professional trainers who compete @ high levels actually are really bad @ teaching people. While other trainers are phenomenal @ teaching the basics to beginners, but will never go beyond teaching that level & maybe don’t ride @ a very high level themselves.
Trainers can be specialized. Some will take on problem horses, while some other trainers send their own young horses out to be backed. Some aren’t that confident to train youngster, while others are too busy with a show career & would only ride horses ready to start in grand prix.
Some riders choose a trainer based on their own personal experience. Then as the rider becomes better they have a stronger eye to evaluate for the next trainer. Which then they will usually seek out a better trainer. One who can challenge them & take them to compete in the next level up.
I disagree with some of the things said in previous posts. A wise trainer doesn’t have problems asking for advice from the ground. Especially if they are having difficulty w/a training issue. Trainers as well as riders benefit from having lessons. There is no point where you just know it all. Trainers continue to learns new things everyday just like everyone else.
The trainer is usually more of a go getter & risk taker than most people.
They are perfectly willing to give up a solid 9 to 5 job ~ to train horses full time. Most trainers are highly dedicated, athletic, hard working & passionate beyond the point of obsession. They usually are the students who found riding to be very natural & they progressed quickly. Training or problem solving came easy for them as they communicated well w/horses from the get go. They were the riders who stood out ability wise & got offered compensation to ride other peoples horses. This is the point where most riders either work as an assistant or apprentice. Gradually moving towards a point where they have their own clients. Eventually leasing their own aisles or stable or partnering w/ the trainer they worked under.