Betting on sports is typically a losing proposition. You may win some bets but, on average, the house wins.
But there is an exception: promotional bets. If you are offered a free bet, it is possible to lock in a guaranteed profit by also placing a correctly-sized hedging bet that wins when your free bet loses. This is known as matched betting.
Here, I have provided Python-based calculators that scan bookmaker’s quotes to get you the best possible guaranteed return. It allows you to do this without paying for the (fairly costly) subscription services that advise you how to do this.