I’m in America.
If you count going away to university then I left my parents’ house at 19. But, at 18 I had already started local college and stayed part of the time with my boyfriend. Actually, I think I might have started staying with him at 17, but I still technically lived with my parents until I left for university. My parents paid for my college education, so I was not financially independent, but I was not living with them anymore, I was a few states away (a 10 hour drive).
After college I moved home for a few months, then moved to Florida to start my career down there. I was 22. I didn’t have a job yet, but stayed with my cousin a couple of months, during which time I found a job, and then a friend a couple of more weeks and then moved in with a roommate.
In my country it varies, but most kids graduate high school at 18 and then either go to college or start working. It’s assumed after high school “kids” will be moving out of their parents home fairly quickly. If they don’t live at school, then the kids might live at their parents home all 4 years of college, and then at age 22 start the process to move out.
I say process, because whether it’s after high school or college, the kids first need to find a job, and then they might save for a few months, then finally move out.
In some families the kids stay much longer. It isn’t very uncommon for a 23 or 24 year old to still live at home, but after 25 people would find it unusual here, unless it’s a unique situation, but the expectation would be that the young adult is able to financially live on their own, even if for some reason they aren’t. On their own can be with a roommate, some cities are very expensive.
Again, it varies though. America is made up of many different cultures, and new immigrant families especially, sometimes have different practices. I’ve had Italian friends who lived at home until age 30. My husband’s Mexican family has an expectation of being dependant on parents until you get married, but his sister who raised her kids in America since ages 5 and 2, was happy to have her kids move out as soon as they could.
In fact, to me it seemed she was pushing for it more than the average American. Maybe because she hadn’t liked the expectation of having to stay with her parents until marriage. Even though “staying” with her parents included living in their American house if she felt like it (the parents still lived in Mexico back then) or going to finishing school in Switzerland, and then traveling several weeks through Europe. She finally got married at age 25.
I don’t know how common that expectation is in Mexico. It probably is different now, my SIL is in her late 50’s. It also probably varies depending on social class.