Good question!
My 19 year old DS cooks family meal sometimes ( 1 or 2 times pw, more if I am am out), takes out bins, brings them in ( if i remind him) sometimes will mow the lawn on request. Has been known to hoover but again, only on request, and not always then ( so say, once a month. )Sometimes clears up after supper if he hasn't cooked, but will try to get away with not doing it. He does help with weekly shop and meal planning. His room is a pit, and he is responsible for cleaning it, it doesn't often happen!
We argue constantly about what he does ( i feel its not enough bearing in mind he has no income ( off to uni in Sept) and doesn't want to find a job, wants to spend the summer lounging.) I pay for stuff for him but only bare minimum now ( new shoes if old ones have holes in, replacement jeans). I feel he should be making more of a contribution, especially since DH and I both work full time. However he does happily take on responsibility for younger brother (13) whenever I need him to without argument.
This argument has been ongoing for a long time. My latest tactic has been to get him to draw up a list of all the household jobs that need to be done on a daily and weekly basis, so that he can see that I am not being mean when i ask him to have the kitchen clean for when I get home from work. The list filled 2 pages, think he was a bit shocked! He did washing up tonight without making a fuss, will see if this works!
My oldest DS has much improved since living away - now empties dishwasher without being asked, puts on washing ( and not just his own) and hangs it out, clears up kitchen, and much tidier generally - acts on his own initiative ( as indeed a grown man should).