Y'all. Don't smoke.
This 5 AM Cursed Zillow update brought to you by Insomnia
I painted a house whose walls were all a rich, warm nicotine brown, except where the furniture and pictures used to be, which revealed a cheerful pale pink. The nicotine was so staining that it bled through three coats of KILLZ alcohol based primer, which till then had been able to cover /anything/ we ever needed to paint. It was the single nastiest job I have ever worked on.
It was a sad story too. The lady who lived there had been alone for fifty years before she died, and you could tell she was a hoarder because there was a timeline of junk piled against the walls as shown by the gradient of nicotine stains.