I ran into this many years ago here in Nebraska.
Back around 1980 I had gone to school with Soapweed and Peachy to learn how to preg-check. When we got home, I needed volume to get proficient at it, as I had heard that to be considered an expert you'd need to palpate say, 10,000 head.
Over the next several years, I checked ours and 3-4 neighbor's cows getting the necessary experience. They always payed me a nominal amount but it was the experience I was after.
Our Vet, who was a fairly good friend, pointed out to me that although it didn't matter to him, I could find myself in court for charging for these services. At the time, I didn't appreciate his comments, but it was the excuse I needed to get out of the business and concentrate on our own cows only. I had easily armed the 10,000 head and considered myself proficient.
I'll never know if this friend would have sued me or not.
By the way, do you know how to tell if your Preg-Checker is happy?
You can tell by all the green specks on his teeth!