The estate formerly belonged to weight-loss expert Jenny Craig, who initially listed the property for $30 million several years ago. Its last listing price was $25 million, though it was no longer on the open market when Gates made the purchase.
The property, known as the Rancho Paseana, includes a racetrack, guesthouse, office, veterinarian's suite, orchard, and five barns.
Gates' daughter Jennifer regularly participates in equestrian competitions, and the family owns another horse farm in Wellington, Florida.
It's a beautiful property, with wide-open pastures and plenty of California palm trees.