If you were wondering if wordpress themes are free, the correct ans to this is themes on WordPPress.org are free and if you are looking to start off your site. That is best place to start.
Now once you have starting to get traffic you can then start to look at paid themes. That can be found on themeforest.net but you have to be careful here as your content may not look as good as the demo of theme. From my experience I have noticed that clients have has been let down once they put the theme on there site and it also slows down the site.
So I don’t recommend buying themes, the best way is to get some one to make the theme for you and for this you need a good started theme for which I will write a blog post about in the future as I am testing a few different themes.