It doesn't take long to get guest bloggers to post onto your site if you want them. My Blog Guest is a great approach to get the writers that you're looking for that are looking for a way to get their site out as well. Just because you have a PR of 0 doesn't mean that you're not going to be wanted by anybody.
Guest blogging is headed in a direction that it has never gone before because as SEO is becoming challenged as a whole, more people are going to be fighting for content and information that will boost their credibility in Google's eyes. Any company should put guest posting on top, IMO even before looking to PPC or FB ads.