A lot of arbs are on football matches. What happens if the match ends in a draw? Can I lose money?

The central principle of sports arbitrage is that you bet on every possible outcome of an event, in order to guarantee a profit no matter what happens.

Therefore, if an arb is found on the 90-minute match betting market of a football match (or other sport), you would place bets on both the home and away teams, plus the draw.