OMG, I think I have been in that house. LOL... It is a nightmare to walk in and see that disaster and then have to try to work in it. You spend more time cleaning then you do actually painting. I had a house with so much grease on a wall it had to be taken off with a heated scraper and a smokers room where it took some pretty amazing primer, stain blocker and many coats to make the black disappear.
Ya, we have just been telling people, we will paint it, but can't take the liability of moving everything.
You have to almost use oil base primer. No other way to get that to disappear.
I know. It is crazy how these stains can keep coming through. Like a knot in wood. Never ending seeping. Are you still allowed to use any Oil based paints there? They have been banned here for interior work. Makes it so fun when you are transitioning a house from oil to latex. There are some great products on the market to create good adhesion now but it is still so much extra work.