The Horse Trailer is built by the player and then used to access the horse market. The horse market is where the player can aquire new horses of varying breeds and characteristics. Upgrading the horse trailer will increase the quality of the horses appearing there.
The horses in the market are renewed a few times per day and replaced with new ones. The player can also pay to refresh them instantly.
In the market, the player can get a summary of each horse. Some abilities will be hidden upon the first glance, though. In order to get a complete insight into the horse's potential and personality, the player can, for a fee, Examine the horse.
The monetary value of the horses are determined by factors such as their breed, age and skills. The same applies to the player's owned horses, which is why a horse's sell value can be increased by training its stats before selling.