If you ask several different homeschoolers you will get several different answers ranging from “No way” to “ABSOLUTELY”!
The short answer: You are not required to join any group to homeschool legally, but a great benefit of joining one is having access to help and legal counsel should the need arise.
The longer answer: It is a personal choice that you MUST become informed about, and it would be irresponsible of us to tell anyone they should or should not not join a legal organization. Most of what you hear from naysayers will be something along the lines of “they are in it for the money” or “I don’t agree with everything they stand for”. But there is another side...all of the people such organizations have helped would tell you they are thankful they are members! Additionally, you will never agree 100% with ANY organization, so it is a matter of what will make you most comfortable.
Some details to consider: Obviously, some locations have more complicated laws than others. Some families have neighbors or family members that strongly disagree with their choice to homeschool. These are just a couple of reasons one may choose to join and feel assured that, in the event they are questioned by a child protection agency or a truancy officer in any homeschooling matter, they have a number to call for immediate help.
Our best advice is simply to read up and decide what is best for your family. There are national and state based associations. Here is a small list of some national associations to get you started, but you should also check with your state organization(s):