Content locking would be a viable solution. Essentially, the user has to fill out a survey or complete some sort of offer before they gain access to the content. It's always a good idea to actually give them the content afterward, but you don't even "have" to do that. But I would... (You get money from the content locking provider)
As for monetizing. If its "enough" traffic, adsense could provide revenue. You can always sell links and blog posts as well, if the SEO is authoritative. Sell clickbank offers, or check out commission junkie. PM me the link, I'll give you some more tips if I can see the site.