I am not sure I completely understand your question. There are no hard and concrete rules if you are repurposing a piece of furniture for a vanity. No it does not need to be raised off the floor. This one was, to help create the illusion of more space since it was a small bathroom. A toe kick will depend on whether you need one or not with the transition from the floor. Is this for wheelchair accessibility? If so you will want to follow ADA guidelines. Hope this helps.
Walls too Windows, Interior Design