What have you tried so far?
Have they ever had a job? gone to college?
What do they want to do with their life?
Are you the mother or the father?
Now is not the time to talk about poor parenting skills, we do the best we can and the best we know how, and parents are allowed to make mistakes too. At this point, if he's not trying to get a job or be a contribution to the house, then you will have to give him a certain amount of time to get it together and find somewhere else to live. For example, you have until April 30 to get a job or leave. He should also have certain chores that he does around the house, taking out trash, doing dishes, anything. You also should not give him any money for anything, if he needs something small (deodorant, underwear) and you feel it in your heart to buy it for him that's one thing, but nothing more than that. He also needs to be in NA, therapy or both. I welcome your thoughts, let me know if you want to talk more