Well, I'm Finnish, and I was always taught it's very rude.
It's kinda like asking someone about their religious views or sex life.
Not really any of your bussiness unless you know the other person well.
(And if you go around telling that to people you're being inappropriate.)
That being said, people tend to have unrealistic image of how much money Youtubers make, so you might want to set them straight. Maybe ot tell them how much exactly, but something along the lines of how many views you need to make any money, or how much you get per view.
It's kinda like asking someone about their religious views or sex life.
Not really any of your bussiness unless you know the other person well.
(And if you go around telling that to people you're being inappropriate.)
That being said, people tend to have unrealistic image of how much money Youtubers make, so you might want to set them straight. Maybe ot tell them how much exactly, but something along the lines of how many views you need to make any money, or how much you get per view.