Pay close attention to your state laws and what you are or are not paying for. Look for information about it from your statewide homeschool organizations on how it affects homeschool freedom in your state. There are some virtual acadamies that are homeschool and some are actually public school at home. The materials are given to the family for free and the child and family are beholden to the public school calendar, state testing, attendence polocies and all other aspects of school that public school families are held to. If you are or have any interest in being a member of HSLDA, they will not permit you to join if the virtual acadamy you enroll in is actually a public school at home or 'government homeschool' (another term I have seen used for it).
Nothing is free, just do research and know what you are or are not signing up for and do the right thing for your family.