When a professional completes inspection of your plumbing problems, you should receive a detailed estimate. Find out about acceptable payment methods, such as cash, check, or credit card. In most cases, homeowners should not have to pay any money before the job begins. For very complex projects, they may ask for a “good-faith deposit” in advance, often 10% or less. Most will call for the full payment after completing the job. Complicated work that takes weeks could mean you make several payments over the course of the project.