Wdym you don't know the person? You don't know their full name but have their face in mind? I think that knowing it's name can help, but it's not fundamental, you can focus on their face and body only. I don't think practicing black magic against someone's house it's a good idea, especially if other people live in it, you can hurt people who have nothing to do with the person you want to curse or the object of your hatred.