No it comes from the seller - its a commission that's done on much the same lines as the way a realtor works.
The agent/trainer will do all of the searches for their client and the seller will make agreement with the agent/trainer for how much commission they'll take from the sale. If they can't reach an agreement they won't take their client to see the horse.
You'll find that that trainers or agents that operate this way will insist on their clients only looking at horses that they've arranged the viewings for
If you do your own searches these sort of agents won't have anything to do with the viewings unless you negotiate a fee for their time up front.
Well, that is a bit different, with the agent actively doing the searching, negotiating the price, which includes his fee, with the seller, having a list of clients, for which a certain type of horse might work, versus someone asking their trainer to come along and see some horses that she is interested in
Then , it is more like PPE, JMO, with the buyer paying that trainer for their professional knowledge,and opinion, where upon they decide to either go ahead with the purchase, or not
I assume that the trainer was not working as an agent for the seller, but was just asked to look at the hroses,by the buyer, and give a professional opinion
Whenever an agent was involved, as when we had some International buyers from Germany come look at some of our hroses, I had set a price on the horse,which the agent had inquired about, and the agent then gave a price to the buyer with a profit for himself included.