I've found that the most challenging part of creating a comic book, for most people, is the artwork. It requires a lot of skill and time, which prevents many people from finishing or even starting their idea.
To solve this problem, I developed a project that re-uses public domain comic books (from the Digital Comic Museum), providing you with an instant layout and artwork, allowing you to spend more time writing the story. The easiest way to use this technique is to take an existing comic and replace the dialogue and narration with your own original writing. Or, since all of the content is public domain, you can even mix and match images from different stories to create your own custom adventure! You can find my step-by-step guide and more project photos featured on Instructables: Fill in the Blank Comic Book
There are also historical comics available in the archive, making this an option for the classroom, as well. In the project demonstrated in the instructions, you'll see how to adapt the project in to an educational activity where learners are expected to read the original of a story, and then fill in the blanks with their own rendition.
Lots of creative options, inexpensive, & easy to do -- enjoy!
Fill in the Blank Comic Book