You'd expect so and it's bound to have been done, it's still one of those domains where the establishment (owners, trainers, breeders, jockeys, track associations, etc) is weighted against outsiders.

Money would count, but I dare say it'd need a bit of crafty social engineering running in parallel to crack in.

Caveat: I'm not a horse racing / polo insider - I did some contract work years back and rubbed shoulders with a bunch of millionaire horsey types.