One page can be enough
A focused business with a simple offer can perform well with one strong page if the page clearly explains the service, proof, coverage and contact options.
Three pages is the CMB sweet spot for many businesses
Three pages create room to separate the homepage, important services or company information and contact intent without creating content just to fill space. That is why CMB often recommends a three-page structure as the strongest balance for many service businesses.
Five pages create more search and content room
Five pages can support several services, a dedicated about/contact path and more specific search topics. More URLs are only useful when each page actually deserves to exist.
More pages are not automatically better SEO
A larger website only helps when the pages contain useful, original information. The goal is to give each important customer question a strong destination and connect those pages through a logical hierarchy.