Another point:
If you have the capabilities and there are no licensing problems in your particular area, try to cover installation of telephone, TV, alarms, and any other similar systems as well as just electrical power.
I've had several jobs in my area where someone has been "doing up" a place and was quite pleased to learn that I could handle all of this stuff so that they wouldn't have to call in a whole load of other people to take care of it.
