For some small town cities it’s easier to use city based landing pages to show up in google's search listings. However, it is against Google's guidelines to create landing pages with the exact same content although this is somewhat open to interpretation.
Doorway pages are sites or pages created to attempt higher ranking in city specific search queries. The reason these can be bad is due to the fact that they can lead to multiple pages that look alike in the search results. And obviously that’s not a great idea. They can sometimes lead users to other pages on the site that aren’t very helpful either. Some of your clients’ competitors probably use them, as it’s a popular strategy.
Sites that are ranking for city targeting keywords with specific dynamic content aren’t necessarily doorway sites. On the site you could point out jobs you’ve covered in that specific area in the past, case studies for that area and other content to make it more valuable to a potential searcher.
By posting rich, informative, and completely unique pages based on the service area location for each page, it does not fall under doorway pages and is adding value. That’s exactly what Google wants in its SERPS. Just make sure all the pages are individual or your client can be penalized. There is a difference between 20 pages for local towns with rich, unique, informative content and 1,200 pages with similar repetitive content.
Users looking for city based results will find this very helpful when deciding what location to choose from especially if your service areas are not near each other. Also with your SAB business, make sure that you are willing to capitalize on leads that may be a bit farther away if you’re using multiple unique pages or it’s all for really nothing.
It changes a bit with how you set up those pages. Now if you advertise you serve the area of Nashville, and then create a page for a suburb of Nashville that’s 3 mi away, that’s definitely not recommended. If your service area has 15 mi or more, that would be more logical to create a city based landing page for that location.
As a general rule of thumb, don’t cut and paste ‘template’ city pages and create unique pages with valuable and informative content!