Now that I read the whole thread, I'll make one final comment on the whole "in writing" thing. Verbal contracts rarely count for anything regardless of the money involved. You ALWAYS get something in writing - whether it's a receipt for a deposit or - better yet - a signed contract agreeing to the terms of sale, including how long the owner will have the horse. It protects both the seller and the buyer.
For instance, say you "buy" a horse, no contract is signed and the seller is holding it for you, and someone gets kicked? Who's liable? Without a contract explicitly saying when the actual transfer of ownership takes place (i.e. When the horse leaves the property, a specific date, effective immediately, etc.), you and the seller may be pointing fingers at one another and end up in a lawsuit from the injured person.
If you were buying a $30,000 horse, I guarantee both parties would be signing detailed contracts before ANY assumptions were made about the transfer of ownership.
As it's been said multiple times, it's business. And it has to be treated as such.