From ebizvaluations

7+ years old
Over 64,000 links
Listed in DMOZ

Obviously he won't sell for the $0 valuation but if it is indeed making a $0 net profit then your own valuation is going to be based on what you think you can earn from the site.

Standard Disclaimer: As usual, this is not a recommendation and I make no profit from bringing these to your attention or putting you in touch with the sellers. Check the books and do your own valuation and due diligence. As usual, I don't compete with you on any prospective site I spot and list here.