You need to be careful hiring without ample references and feedback from past employers of your potential assistant. A little research online will give you an idea of what other people have experienced and what to be careful of. I suppose that starting with VA's through a mediator (guru.com, freelancer.com, Amazon's Turk, etc.) may provide you a bit of a safety net and arbitration if the need should arise.
I am working on 3 platforms myself that will provide the most effective and simplest way to acquire VA services for every budget (as I use the system for my own network of sites and for my customers).