Having a virtual assistant is the new way of doing business, you are thinking practically.
Advantages and Disadvantages work either side the way you initiate the process.

As you have asked for the advantages there is surely a list to it, its as follows:
1) Healthy to your pocket, as you hire a virtual assistant for the duration you actually need them for.
2) You save on space-cost as all work is done in their space, and the best part you aren't paying for it.
3) The virtual assistants are really productive as they are working in their comfort zones.

Surely, there are disadvantages when you hire a virtual assistant. But I could help you be well prepared with the appointment pattern, process of daily work, target mentoring etc.

Do let me know if you think you need my support to have a strong system to have a virtual team.