Ok, suddenly the casino you're playing asks you for proof of income to be able to withdraw your winnings and to keep your account in good standing, your bankroll every month is $500 and you provide proof of salary that you are making $500 net every month, will they accept that proof will they accept that you are putting all your salary for gambling, will this violate the principle of gamble for fun, because you are working to gamble based on your proof income.
I think
they don't even have the right to prohibit you from gambling even though your money in gambling comes from your monthly salary, of course, this will be a bad habit if you play your monthly salary for gambling. But back to the point I mentioned (bold text). Then, I also wonder, on which site do you play? is this a physical casino? I also want to know more about this. But whatever it is, if what they are asking for is an obligation to withdraw money, like it or not you have to provide the data they ask for.
You are confused. Just because he has a bankroll of $500 doesn't mean he bets $500 every month when his salary is the same amount.
With a $500 bankroll he can make $1 bets and thus minimise the risk of going bust.
When he says that he has a monthly bankroll of this amount, the most likely scenario is that if on the 1st of the month he has 350 dollars left, he puts 150 dollars out of his pocket to complete the 500 dollars, and if for example he has 600 dollars, he withdraws the 100 dollars left over to spend it.