Use the tape measure to determine the number of linear feet you need to purchase. Measure the length of all of the roof sections where you want to install guttering and add them up. Don't forget to measure any small corners where you want guttering, as it's better to err on the side of too much vinyl.
Look up a vinyl gutter cost calculator online. Enter your ZIP code and the total from Step 1, and click "Update" or "Calculate." The purpose of the ZIP code is to let the calculator access average materials cost in your area, which varies significantly throughout the United States. Some calculators will give you one set of expenses, while others will give you a range, depending on the quality of materials and installer that you want to use.
Perform an Internet search for a roofing contractor in your area. Your homeowner's insurance provider may require that you use a licensed contractor to complete the work, so check your policy to make sure. The Better Business Bureau offers a search tool that you can use, and most areas have a contractors' association with a website that will assist you.
Choose several different contractors to secure estimates for the cost of the job. Most contractors won't provide an online estimate, but you can look on their websites for contact information for references from satisfied customers. If there aren't any, you can ask the contractor for references when talking on the telephone. Access sites such as RipoffReport.com to see if your contractor has been the subject of complaints.