A respiratory mask, eye protection and gloves should be used when attempting to remove the problem. There are many products than can be used to remove the substance. The most common of them is bleach.
I would suggest you to only open a door between the two bedrooms. My uncle has this kind of room and I think it would be better if you would have this.
In my opinion, that house is just good and all you have to do is to repaint it. Or much better, ask the seller to fix the damages first before selling the house.
