I am not a fan of smoking. At the very least, smoking inside the apartment will stain the walls, and will require that I paint the walls when the visitor leaves. With that in mind, I will expect any overnight visitor to smoke outside if they should smoke. This will keep the walls clean, and reduce any chance of the dangers that smoking can cause inside (such as falling asleep with a lit cigarette). If I was to foster children, I would not want any child that smokes.