10% is the usual commission + travel. When I was an agent, that meant finding horses to try, researching them to see if they would be suitable for my client, traveling with the client to try them, negotiating the price, organizing the vet exam, acting as a go between with the seller and buyer, finalizing a good contract, and arranging transportation, if necessary. Sometimes it meant going to see horses before the client came in to town to make sure I was presenting suitable horses. Occasionally, I would need to help when things did not go well after the sale. Agents EARN their commissions!
As a buyer, when I handle all of the above, I do not expect to pay a commission to my trainer. However, sometimes the seller, especially if they are a professional, will pay your trainer a commission. Nothing you can really do about it. I do go in to negotiations saying that there is no commission on my end. It usually gets you 10% off immediately.
There are some trainers who insist on a commission, just because they teach you, even if they did nothing. There are others who want 10% because they gave you a phone number. I hate that. The buyer’s agent and the seller’s agent, who do the hard work, are the ones who should get the commissions. Its a twisted world, and some buyers end up spending more on commissions (unknowingly) than on the horse.