Lighting is a field of it's own, a bit more then just hanging a fixture is involved to produce the correct effect, and deliver the level needed, there are a number of lighting courses offered by manufactures and lighting engineers, I recommend anyone planning on doing lighting projects, look into these offerings.
When your selling lighting, your selling more then an installation, for example, a commercial customer may want lighting to bring out a color or detail, or hide a color, or detail, lighting placement can be a critical factor in commercial locations, if you don't have the skills to provide these services, you may be loosing out on a large part of the lighting market.
One of the courses I attended, they had two tables of food, with overhead lighting, one table the food looked great, the other table the food looked like something ready for the dumpster, as it turned out, the dumpster food was really the good food, and the other table was the spoiled food, amazing what the proper lighting for a project can do.
