The heading of your post states that you wanted to prepare an "HR Business Plan," whereas in the body of the post, you mention wanting to create a general business plan. Could you clarify your specific requirement? There is no distinct concept as an "HR Business Plan." You may want to take note of that.
Previously, there was a discussion on a similar subject, and I provided components of a business plan. You can refer to it by clicking the following link:
https://www.citehr.com/339378-busine...ml#post1627638
Thanks,
Dinesh Divekar