This job is usually done by a professional house painter. The painter will assess the walls, clean, and make any necessary repairs or removal of old wall coverings. They will also tape off any adjacent surfaces and cover nearby furniture and floors with drop cloths. Typically, they will apply a layer of primer, then one to three coats of paint, depending on the color and coverage. Once the paint is dry, they take a final walkthrough to inspect and make any necessary touch ups.
With an exterior paint job, proper preparation before painting is essential for the paint to withstand the elements over time. Preparation may include sanding rough surfaces, patching holes, dents or cracks, caulking around windows, and priming all surfaces before painting. Proper preparation will have a big impact on the finished appearance and how long the paint will last.
Even if you go it alone, specialize to keep your initial investment low. If you do only interior painting, for example, you might get by with one ladder, a few brushes, rollers, basic hand tools and such, for an investment of less than $300. Again, you can add to your tools as you need to (every job is a bit different), and parlay profits into the equipment necessary for exterior painting or working on large commercial properties.