It's been a busy couple of weeks. I had a young Singaporean guest from Sydney staying for two weeks. Then a couple of Korean mates coming to stay with two kids.
Really, anyone who is 20, and tells you that 'people think they are really mature' should be taken with a pinch of salt. Especially when they throw their stuff all over the guest room, doesn't help out until asked, or help to clean up when you have cooked meals for them. In fact you have to do twice the work after their arrival.
Whereas one who is in their late 30s who cook, clean, and dry up after themselves know much about being a good guest. So much so that you don't need to say anything.
Someone in their early 20s have to be told what to do, and what to expect. Due to lack of experience of probably staying with others, or mentoring, they really do not know what is required.
Anyways, it's good to communicate your expectations and requirements when allowing or having a young guest stay in your place. It will do much good for their social skills in future and they will thank you for it.
It will make them a much better house guest, and they will get a return invite to stay in future.