This is one department which must be justified to the maximum for a healthy business. You must not let any stone unturned to satisfy your customers. One issue with such jobs is that the result comes out in a fraction of seconds and if you have done the job right only then you will be able to get the money you have demanded. So this makes plumbers job a really adrenaline test. There is no need for advertising a lot to get a handsome business just give your best shot to the jobs you get and your reputation will spread like the jungles fire.