Test before you scrape
The costly mistake is soaking and scraping a ceiling nobody tested. If it holds asbestos, the fibers end up in the house, and EPA advises against sweeping or vacuuming suspect debris. Sampling first avoids all of that.
A positive ceiling in good shape can also stay where it is, provided nobody drills or cuts it. Just keep in mind that it is still there, because a later light fixture or repair will disturb it.
Ceilings are one material among several; for the walls, read Drywall, plaster and joint compound. Dallas Asbestos Removal's homepage has links to every other page.