A number of our clients have been contacted by link-star offering to place advertising on their website in return for an annual fee. There are a number of postings on websites about this type of scam e.g. see http://blogs.computerworld.com/seo_text_link_scams
If you did go along with placing the advertisement you could well be going against Google’s terms of service and your website could be blacklisted by Google.
It is quite unlikely that a small business website would generate enough traffic for a legitimate advertiser to be interested in it. The purpose of your website is to generate business for yourself – not for other people!