I have to agree with Tess completely. I think the outreach to potential clients can only be done by yourself since your first impression is everything. Part of being a virtual assistant is building relationships with your clients and that really needs to start from day one.
However, if you are thinking about sending out cards or something similar, that doesn't require you to actually speak to someone, that sort of thing could be outsourced. I recommend a service called Ask Sunday. Their website is
www.asksunday.com. I believe they are relatively cheap.
Hope this helps!!