In order to start the process of lesson planning, you need to know how much time you are planning for; in other words, what is a school year for your homeschool?
First, determine the total number of school days in your school year.
There are two factors you need to consider when making this determination. One is the number of instructional days required by your state. Even the least-regulated states have a requirement for the minimum number of days of instruction for the school year. Typically, this is 180 days, but some states require more, some fewer. This is the minimum number of days for which you must plan.
The other factor you need to consider is the number of days that will be required to move through the longest curriculum that you have planned for the upcoming school year. If that "longest" curriculum will require less than the minimum number of instructional days, it won't be a factor in defining your school year. If it will require more days than the minimum, its length will determine the length of your school year. For example, suppose your state requires a minimum of 180 days of instruction. When you examine your curricula for the upcoming year, you find out that one curriculum, say algebra, will require 200 days of instruction to complete. Your school year would then need to be 200 days long.
Be aware that you should expect different curricula to require different amounts of time to complete, and that many won't "come out even" with the school year. Also, some curricula aren't designed to last the entire year, but might be intended for only a couple of months of instruction. There is no requirement that you must be doing the same set of curricula for a student every school day, and the odds are that you won't. You will complete some curricula while you are still working on others. Your lessons plans might call for starting some curricula sometime during the year, say successively after you complete another one, or concurrently.
After you have determined which is more days, your state's minimum number of days of instruction or your longest curriculum, you will know the total number of days in your school year. This becomes the total number of days for which you must create lesson plans.