No you don’t pay both; WordPress is a free platform. What you’re looking at on the WordPress website is their hosting service costs. You’ll be able to upload WordPress directly from BlueHost. There are free options but you’re limited in how you can monetize. This post has some information on free options: https://www.theworkathomewoman.com/businesses-start-no-money/
If you want to set yourself up for success, then you should invest in a self-hosted blog. A self-hosted blog is when you pay a company such as Bluehost to “park” your website in their “parking lot.” The company owns all the servers that you’re able to use to host your own content on (i.e. your blog). This service comes with a monthly fee of course.