It is normal for young adults to want to get out on their own - and it's healthy too. Living independently actually builds independence and personal confidence. It gives them an opportunity to learn about money management, time management and stress management. It helps prepare them for adulthood and real responsibilities. Even if you help out financially, there are many benefits to your son to be spreading his wings. However, at 18 he is still quite young. You don't have an obligation to support this project financially. You can tell him that you would rather help him out in a year or two  (if that's how you feel) or you would rather that he moves out when he can fully support himself - it's your choice. If you decide to help him out, however, I do not see any downside. On the contrary - I think it could be a great learning experience for him.