Typically 5 years of administrative experience in an office is expected at such positions as executive assistant, secretary, legal assistant, paralegal, legal secretary, real estate assistant, office manager, etc.

In the interest of full disclosure I'm a close family member to someone who specializes in providing actual virtual assistant services to the legal community. The founder of Legaltypist thinks the Wiki definition is too narrow. Legaltypist prefers this definition:

Virtual Assistant:

A Virtual Assistant (VA) is an independent entrepreneur providing administrative, creative and/or technical services.

Anything more specific falls under the umbrella term "Virtually Assistent," The wiki definition is attempting to be to exclusive. Providing secure communication, dictation, legal documents, office management, billing, running the whole gambit.