Welcome to Gaia! ::

There is this horse that I might help trian to barrel race. Ii am still thinking bout it and haven't decided if I should or not. Please give me some input about it.

Well, it depends. Does the horse have the right confirmation? Personality? What are they already trained to do? Who are you training the horse with? Do they have any experiance? Do you? One of you should have at least some experience in traing horses. Some times magazines (such as Horse Illustrated, and Young Rider) might have tips. the horse should be supple before you start turning barrels.
That's just what I can think of, there's probably more.