For example , you are betting on a football match, you can bet on Team A on one betting site, Bet on Team B in another betting site and also bet on a draw in third sport book.
I don't know how can you be in overall profit as you will only win one bet out of these three bets (in above example) and you cannot gain profit through arbitrage betting in most of the cases.
You can earn guaranteed profits actually by betting on all three outcomes through 2-3 sportsbooks using arbitrage calculators and splitting money correctly. However, this sort of stuff could easily get you restricted which is why it's risky.
Most punters who earned money through arbitrage betting employed successful matched betting strategies and earned sizeable profits which they were allowed to withdraw.
Their bet sizes would get restricted, but they still end up earning huge profits overall.