Things have been really busy here at Makespace this spring, with several client website launches. One critical milestone that clients usually struggle with is content strategy. Obtaining website copy from web design clients can be a difficult process, partly because clients often underestimate just how much content is needed to create a robust, search engine friendly site that will position them well in the search engine results pages (SERPs) for their most important keywords.
Many SMBs, if they've had a web presence previously at all, have had a basic "brochureware" site, that consists of about 5 web pages, with minimal web copy.
While a simple brochure site is easy to launch, they rarely rank well in search or get a high volume of visitor traffic.
Remember when you're contributing content or source information and resources to your web development team, that your web content serves two purposes. The most important purpose is obviously to convert your website visitors to customers. However, in order to do that, you first have to attract visitors to your site, and the most important way to do that is to capture them from the search engines. Which means the other purpose of your content is to help your website rank well.
For this reason, it's important that you have sufficient volume of content which includes your most important keywords, worked in as naturally as possible. Google also rewards sites that have fresh content; so in addition to having enough content to launch, it's important to refresh and update your content frequently in order to continue to build and maintain rankings.
No one aside from Google's engineers know the magic number when it comes to how much copy is enough to ensure your site ranks well. It depends on a number of factors including what the specific keyword you're targeting is, how much competition is out there, and several other criteria.
A good rule of thumb, though, is that it will probably require more than you expect--so it's a good idea to give your web agency as much help as possible by providing resources and feedback in a timely and complete manner.