The free version includes the JLPT level 4 words as well as the phonetic Hiragana and Katakana sets. It's a great way for beginners to get started, but also enough for you to see if Read The Kanji is an effective study tool for you.
The pay accounts offer full access to the site, including all stats, current word decks, and future word decks. Our Yearly plans are priced for students looking to study Japanese in the long term, whereas our Quarterly plans are set for students who just need access to help prepare for upcoming exams.
If you'd like to upgrade a quarterly or yearly plan, you can change your plan in the user preferences menu at any time. It's just a matter of choosing the plan you want, and entering in your billing information. You can also downgrade to any plan at any time with no extra charge.
If you decide to cancel your account, you won't be charged again, but you are responsible for whatever charges have already been incurred for the current billing period.