In this context sight has a couple of meanings. The first is like the sighting of land from a ship. The sight of the house is a glimpse of it. The second is simply the condition of the house.
I might tell my kids, “I can’t stand the sight of your room right now.” Which means I am upset by viewing the condition of their messy room.
Someone who has viewed only the photos could be argued to have seen the property, yet still remain sight unseen of the property