If the wallpaper is vinyl you might have a chance because just getting the wallpaper wet will not wet the backing behind the paper. This is why we usually just dry strip the top layer and then saturate the backing and paste before removing that. But yeah, it is probably going to be difficult to remove just the border without damaging the wallpaper behind it.

The house is 100 years old. So, 1. Make sure walls are indeed plaster. (peek behind outlet cover?) 2. See if vinyl wallpaper can be pulled off (I'm sure it's decades old). If not, do I go to steps 3. scoring the paper, using gel stripper, etc. 3. Best case scenario, how much time are we talking? Remember that it's a rental, and rental time is only one year. I'm scared that I start and then reach the point of no return... and end up with a wall that needs skim coating. Now, my impression is that it's very thick vinyl wallpaper, probably installed in the 70s, 80s. It feels plasticky, with a texture, and definitely scrubbable. Because it's heavier than normal wallpaper, I'd assume that it's been attached with a heavier paste. Is that going to be a problem regarding removal? How can I figure out what paste was used?

It depends a lot how the paper was put on and what kind of adhesion was used how hard you will work to get it off. When you wet it and warm it you want to get it to the point where the paper lifts right off. The issue after that will be the remaining glue. This is where it can get really hard to completely get the glue off to the point where you can paint it without disturbing the lead paint. Also, one thing you may discover is that you do not have a fine finish that will look good painted on the plaster underneath, and that there is in fact no paint at all of any kind in some rooms. They will need a new skim coat anyway. It then becomes: do you have enough glue off to adhere a skim coat? Whatever you do, just be careful. People get all bent out of shape about asbestos and mold but neither of those are really much of a danger in an acute exposure situation, but "lead stupid" is forever . It dissolves in water, it can get dispersed in the air, etc. and if you get it all over the place it can get VERY expensive and hard to clean it out of the house afterward.

Sorry to hear about your experience. Mine is/was similar. I found several layers of wallpaper, with a skim coat in between, and then under that, it seems to have been applied directly to drywall. I have removed a lot of wallpaper in the past, but I ended up damaging the drywall in one room so badly, we decided to hire someone. I had several contractors come through who looked at the amount of wallpaper and wouldn't do it! One guy was willing and he starts this morning so I will see what magic he uses. If he has any tips, I will share.