No, content doesn’t grow on trees. Content is a valuable commodity—and perhaps more than a commodity. Great content is wonderful and unique, and not fungible.
Communities can supply a great deal of content if you have an idea for a good framework that will entice contributions about specific subjects.
If you are a writer, you can create content yourself. (Maybe this is the time for your inner writer to finally come out!)
Site owners can hire writers, either as employees or freelancers, or with a profit-sharing arrangement.
You can often pick up the rights to publish material on the Web that was originally created for a book, magazine, or newspaper very inexpensively. Content creators may be placed to let you use their content simply in exchange for publicity—in the form of an author credit as an expert and/or a link.
You also might check out book and literary agencies—some of them run a sideline business supplying aggregated recycled content, and represent whole groups of writers.
So even if you aren’t confident that you can personally create valuable content, don’t despair; there are many inexpensive ways to publish valuable content without writing it yourself.
Don’t underestimate the value of resource pages as content. A simple page of links to sites related to a specific subject (for example, sites of interest to collectors of antique typewriters and calculators) may draw traffic if the links are accurately described, kept up to date, and expanded when new relevant sites are opened.