From what I have seen it is possible to make money out of it BUT:
1. You need to have a lot of different bookmaker accounts with all the various bookmakers (many overseas).
2. You either need to leave significant amounts of money in these accounts OR you need to transfer large amounts to the accounts you need to use for each opportunity

There are therefore some risk with your money exposed to possible loss if one of the bookies went bust. Also if you have to pay a fee on deposits or withdrawals then that can eat up most of your profit.

The profit margins are quite slim (usually only a couple of percent) so that doesn't leave much for expenses, etc.

Also you need to be aware that with some sports the rules between bookies are different so what seems like a sure thing can end up losing you a lot of money. For example with Tennis different bookies have different rules for voiding bets in the event of a player pulling out of the match injured. In the event of an incomplete match you could find the bookie you backed the "winner" with cancels the bet whilst the other bookie declares a result so you lose your money there.

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