Even if you have only home educated for a short time, you have most likely encountered the skeptic who asks, "How are you going to teach (fill in a difficult subject)?” Or, you may even question your own ability to teach a particular subject.
Most homeschool parents are, at least, high school graduates; many are college graduates. You have more knowledge than your student. It has been said that you only have to stay one day ahead in a subject to teach it. If you don't remember a subject from your school days, study one lesson (or more) ahead of your student and teach as you learn.
Additionally, you may discover that you love math, science, or history. Many home educators have discovered that they love teaching a subject that they hated in school. The subject comes alive for them when they research it to teach it or learn it alongside their children.
What about subjects that are truly more difficult for you or you have no desire to learn, but your student does? You can outsource some subjects. You can hire a tutor or find a class at the local community college. Online classes and co-op classes are also available for many subjects.
Do not be afraid to let your child forge ahead in a subject that you do not know. My children are far beyond me in their computer skills and knowledge. I don’t know about you, but my goal is to encourage independent learners, not mother dependent learners. When my children ask me a question and I instruct them to research the answer, they are never quite sure if I don't know the answer or if I think they will remember better by doing independent research.
You are the expert for your child. You know how they learn and what motivates them. You can teach what you don't know or find a way for it to be taught to your student. You are an expert at finding answers. If you aren't, you can become an expert answer finder and help your student to do the same.
Are there any subjects you don't particularly like to teach or are afraid to teach?