You will not know because they will not tell you; they will always come up with excuses that will convince you to give them that money, or they can even boldly tell you that they want to gamble with it, not that they don’t have the money but that they don’t have access to it for the main reason that you should lend them the money later in the day and they will send it back to you. Things like that do occur.
When a gambler tells you he's borrowing money to gamble, he's implicitly warning you that if he loses, repaying the loan might be difficult, and you could end up sharing the loss. As someone with my mindset, I should be cautious and well-informed in such situations.
Yes but I think it is very unlikely that they would tell a borrower that the money would be used for gambling, because in general people are usually reluctant to lend money to gamblers even if they are gamblers who have good responsibility in their gambling activities or in the sense that they are gamblers who can maintain and control themselves well. This is because there have been quite a few cases that have occurred that it is really difficult for a gambler to be accountable for the decisions he has made such as borrowing money which in the end usually means that they run away from responsibility.
And maybe this is the reason why gamblers are usually secretive about what the money they borrow is for, usually they lie and say that the money will be used for something else which can also be a plan or scenario that looks desperate so that a borrower feels sorry for them and gives them a loan. This means that I think it is quite difficult to really identify what the money is being used for, unless the person is a very close friend of yours who you usually know about their habits.