Begin prepping your walls by removing any outlet covers or lighting fixtures (if possible). Next, inspect your walls for any defects. If you encounter cracks, dents, or holes in your walls, simply fill them in with caulk or spackling compound. There are also a number of DIY tips to fill nail holes. Once your repairs dry, smooth them down with sandpaper and wipe the walls down with a damp sponge.
Similar to exterior mold, mold is more likely to emerge in warm and humid areas. That being said, rooms like bathrooms and basements are more prone to mold. To preemptively prevent mold, use paints that are mold resistant. Should you find mold on a wall in your home, you can clean it with a simple solution of one part bleach to four parts water. If the area is large, you may want to leave the cleaning to a professional.
Most of a projects price is the cost of labor at $25 to $75 per hour. However, most contractors bid out based on the entire project which includes all work hours. Hourly rates are only useful if your pro asks to do the job as “time and materials.” However, be wary of this pricing structure, it usually shows the contractor is uncertain how long the project will take.