In conclusion, while gambling can be an income source for a select few, it requires substantial intelligence, strategic planning, and a dedication to mastering the nuances of the games involved. For most people, however, reliance on gambling as a main source of income can be risky and unsustainable.
I don't think it can be a source of income as a player, in a long run even for selected few, when you say a source of income you mean you rely on it for a living, its hard to do that because of the risk and uncertainty of a bet, a source of income is something that guarantee of income.
Everytime a gambler put a bet he is not working for a living, its taking a risk and hoping to make a profit.