Even the so called professional gamblers are rich people who gamble what they can afford to lose. They do take a lot of losses but because they have deep pockets it doesn't show, plus, when they win, the win covers most of their loses because it's usually a high amount. There is no way you can see gambling as a steady source of income and not lose massively. It might even wreck you so bad you'd be deep in debt. Gambling is like alcohol. Drink, but drink responsibly. Gamble responsibly.
One good thing about this professional gamblers is that they are not greedy type of gambler, when they bet, it will be in an amount that will be huge with small odd like 2.5, they can used that probability event to turn millions into millions and there games are always selective, they also don't gamble on matches that are demanding and popular like final matches, they pick there matches in leagues that are not too serious and not too lazy, this is how they make their millions. However, if it were to be an average gambler that want to bet, he will go over 100s of odds to play a thousand to win millions, they are usually blind by greed to see prosperity.