When installing in-wall speakers, use a drywall saw to cut the hole. A utility knife will make the cleanest cuts in drywall, but a utility knife can be difficult to control by a non-expert. Electric rotary saws make cutting drywall physically easy, but they too can be difficult to control. A simple, inexpensive drywall saw (about $10 at your local hardware store) is the best bet for beginners. The speaker's frame will cover up any rough edges.
If your home inspector discovers a serious problem, another more specific inspection may be recommended. It’s a good idea to consider having your home inspected for the presence of a variety of health-related risks like radon gas, asbestos, or possible problems with the water or waste disposal system.