What type of rules and boundaries have you set up with your adult children?

A lot of adult children live at home, and there seems to be a good comprehensive source of lists about healthy boundaries regards these adult children.

But what about adult children that are not at home? Where do you draw lines in terms of their needs? What types of behaviors would you not accept from them? For example aggression or anger. If they ignored or lashed out due to you deciding not to accept negative behavior what would you do? Not speak to them? (You can hardly punish them right?). If their behavior became destructive to themselves or others how would you handle that? (Since they are now adults). What if this could in the end cause them to become homeless. Since maybe they will not work or take life seriously. Would you just leave them to be homeless?

Some of you may have personal experience of such, some may know someone who does, or some might just have ideas on how to deal with the above. Any feedback appreciated.