That is definitely possible, and basically very easy. However, in spite of saying that, it is actually quite difficult on two levels.
Writing for the Web
Firstly, writing effectively for the web is a complex task. Just because one puts something on a web page, does not mean that people will actually read it. There are many factors to consider. Then in addition, the way WordPress presents information is conceptually different from traditional websites.
Secondly, there are the limitations imposed by HTML – you quickly discover that you simply cannot lay out a page as you would like. If you stick to the basics you get lovely, consistent-looking pages (i.e. boring). Try something fancy, and you get grey hair very quickly.
With a content management system (CMS) like WordPress, it is certainly possible for clients to write their own content for their websites. But know that there is a learning curve. If you accept that, then it can actually be fun – and if things go wrong, I am only an email away!