Why Do I Need a Show Herd?
To make money (HBs), you have to show your horses regularly, including showing the ones in your primary barn. You might check out the auction, looking for horses in their mid-teens, especially neuters, and try bidding on them.
The showing bonus is based on the total number of points all your horses have gained from showing, and those points go with a horse when it's sold. I believe that in this game, the showing bonus is 75% of your total points, divided by seven, since it's paid out daily. So it will increase a bit during the week as your horses are shown. If you want to know the potential of a horse you're interested in buying, take its total points times .75. This will give you its weekly bonus.