Using the very common "Money back as a bonus bet" offers available on several bookies, regardless of where your horse finishes, you can guarantee a profit on 2nd/3rd refund offers using this calculator. Always ensure there is enough liquidity in the place market before placing bets. This shouldn't be an issue on group races within 5 minutes of the race start time.
Whilst this is an entirely Risk-Free approach, it is by no means one of the easier methods.
Please take a look at this guide to see how to use this calculator to your advantage.