How much money do you have to lose before gambling becomes a real problem?

No exact amount. You have lost too much money when you think more gambling is the best way to win it back.
What u can't afford. It is not a matter of how much money, but how important that money is to you. Very rich individuals may not have a problem even if they are losing large amounts of money, but poorer people who cannot afford to spend anything, may have a problem if they gamble at all, including scratch tickets, bingo etc. Gamblers anonymous website may help -.