There is no law broken when someone sells a slow dog. A Your only costs would be agency fees, such as registration of your dog and your racing license. The owner earns commission when the dog finishes first through fourth. A Most tracks now have direct payment. This means the track pays you on a weekly basis.
Most kennels pay every two weeks or monthly.
Like any business, you are taking a financial risk. As a new owner, you should fully understand the hazards before investing. Also, some just don't live up to their genetic potential. A The big tracks are those that do the most handle which means the commission is higher. However, the competition is tough.