Complex sentence: Considered to have little racing potential, he was sold for $2,000 as a yearling, and at age two his owner tried to sell him again but was rejected by an auction company who deemed the horse unsaleable.
Split into simpler sentences: Considered to have little racing potential, he was sold for $2,000 as a yearling. When he was two, his owner tried to sell him again but was rejected by an auction company that deemed the horse unsaleable.