I know that the overall expected value of sports bet is negative, however this is not as straight forward a system as scratchcard for instance.

I am not asking whether it is a good investment to put money in sports bet, I am just wondering if there are people who actually make a living of it. 

I am not talking about someone who won one bet that he lived off of his entire life nor bookmakers or the people who actually manage the bets. But people who have demonstrated through the law of large numbers, that there expected value when betting on sports was positive.