Although you can access many great features on the free plan, including adding a messaging system and pop-up in just a couple of clicks, much of what makes GoDaddy a great platform (namely a ton of extra marketing features) are kept under the lock and key of a premium subscription, which is fair enough. Upgrading for these extras is simple, and prices start at just $10/month.
Just imagine Medium shuts down as did Posterous back in the days (which was a similar service). You will not necessarily lose all your content but all the SEO rankings you ever created. To get it right you need to publish on your own domain name and preferably on your root domain (www.yoursite.com/blog) and not a sub-domain (blog.yoursite.com). This has numerous SEO advantages.