Im interested to know what the most profitable plumbing jobs are? Obviously, large scale commmercial jobs would be excellent if bid appropriately, but Im wondering about the day-to-day medium sized jobs. Where do plumbing companies make the best money? On what types of jobs?.--Answer1:Establishing relationships with client and there needs is your ticket to freedom in any business. Repeat business and referrals from happy clients is where you profits are.Regular scheduled maintenance in homes and commercial buildings are useful contracts to have ~ however, these usually come along with the original installation work as an option.all the best to you ~ its a great trade ~ of the many tradesjust remember, its not about the pipes, its about the people with the pipes and youll do fine.--Answer2:Emergency jobs at 2am when pipes are broken. When people have a crisis, you can charge them as much as you want to.