I signed up for the trial with Zero Risk Arbitrage and will tell you my experiences.

They send out many emails per day, 30-40 with multiple bets per email. I would log into the bookmakers to check the prices and they really were legit.
Unlike the other arb providers which all seem to sell second hand news, Zero Risk really does have an automated scanning feature and the bets come faster than any other.

The subscription cost is 400 pounds a quarter. You averge gain will be 2-4 % on each bet, risk free.

But there is the issue of proper capitalization which needs to be addressed. If you place an allup bets of 1000 pounds and get back 20 pounds, that is good but be aware that money will be tied up until the game is played, its not like you will be able to bet on every single game that comes along.

I did the sums and would have required an account of about 10k at least in order to replace my current income.
Because you need to place the bets quickly it is not something you can just do after hours, you really need to be sitting at the computer all day.

Another thing to be aware of is like someone mentioned earlier, if your bets get to big then you will be noticed and have your cieling crippled. Zero Risk gives ratings for all the bookmakers but suprisingly to me not many of them like bets any more than 500 pounds.