Sometimes you'll think a vendor is selling you content when, in fact, all you're getting is permission to link to content on their site. But if you end up deciding to end the contract, all the content goes away and you end up where you started. Ask if you're actually buying the content to keep, or just leasing it. Ask if the content is on your server or is it just a dressed-up link. Another thing to consider about content that resides on the vendor's server is that your own site won't get caught by the web directories and search engines because the content isn't really on your site.
Many search engines look for key words on a site for their listings.
If the content is not at your site, your site won't make it to the search engine. Since most people still use search engines to find content, they won't find you even if you're paying big fees for the content. Even sellers of content have often bought it from someone else. Find out who is the ultimate source of the content and look at their credentials. Early on, content was the whole point of the web.