Not necesseraly a scam but finding an arbitrage situation or middle is a rare thing to do. In order to make money at this you would need as many outs as you could find. Lets say 40 books. Then you would have to open and fund the accounts. Then you would spend the better part of the day looking for arbitrage opportunities. Once you find one you'd have to make it worth your while so would venture to guess that at least you would have to wager 2 grand on each side. For middles once you find one it doesnt mean that is going to hit. Middles are hit less than 5% of the time. Meaning that 95% of the time you loose out and pay juice. Yuo need a lot of cash and manpower to make it work. If organized crime isn't doing this already, it means its not worth the trouble.