Wallpaper is ALWAYS an unknown, it may come off quickly in big sheets doing no damage OR it might come off slowly in tiny pieces tearing up the drywall in its wake. In the latter case there's an option most are unfamiliar with. By creating a barrier between the wallpaper (water soluble) and any future water based products we can avoid the need to fight and cause further damage to the walls, the pic shows just such a job. After spending a short time fighting with the paper we chose to apply Sherwin Williams fast dry oil primer (barrier) to the walls and then float out (repair) the wallpaper seams. Once sanding was complete the walls were painted as normal saving this homeowner a ton of $$ in time/repair work (charged hourly).
The job was completed in about 10hrs.