Bookies and betting exchanges will take commission too. This kind of betting is not particularly lucrative.<p>Better systems involve looking for unusually high odds by comparing across exchanges&#x2F;bookies, backing&#x2F;laying, waiting for them to swing back into favour, and backing&#x2F;laying to lock in a profit regardless of the outcome. You can back&#x2F;lay to minimise your losses if the odds don&#x27;t swing as much as you thought. Other systems involve backing all possible outcomes (Team X wins, Team X loses, and draw - for example) across multiple bookies such that you guarantee a profit.<p>A good way to start and dip your toes in the water is matched betting. Place bets at bookies and LAY the same outcome at an exchange - do it right and the net loss will be a few pennies&#x2F;cents. Use this technique to syphon money out of bookies offering free bets for new accounts. How much you make is limited, but I made a few thousand doing this at university.<p>edit: Matched betting isn&#x27;t useful only for free bets mind. You can use this techinque to take advantage of some promotions too. One story that comes to mind is a friend who matched bet on horses. The offer was that if you bet £X for Y horse to come in 1st and the horse actually came in 2nd - you get a £X free bet up to a limit of £350. He did four or five times that day. Two times his horse came second. The other times, since the bet was matched, he only made a small loss (less than £5).