Interior paint jobs begin with surface preparation. How well your walls, trim and ceilings turn out will be a direct result of what goes into preparing them for the final paint. Drywall changes over time. Protruding nails can show up as small bumps over time, cracks from foundation settling and other causes can slowly but surely deteriorate the appearance of a once-beautiful paint job. Depending on your time and money budgets, house painting can become a weekend job that can last several weeks or even months, or can last a week or two as a full-time endeavor.