The core process here is to brainstorm – once you understand what the public domain is about and get a clear idea of the sort of information available in the public domain, you can then sit down and brainstorm the different sort of niches suitable for public-domain driven businesses.

Here, instead of finding a business idea first and then finding the right public domain resources, we will look at finding public domain works and creating businesses out of them. But, you'll need to make sure that the right market exists for any of these topics before you start running with the idea!

History is one such category where public domain materials are readily available.

History has always held a deep-seated interest for many people. Whether the interest is topical (a la Da Vinci Code), or long-lasting, there is a lot of money to be made through the public domain. The key here is to find the right target – you can either have informational websites (the most common and easiest business model to set up) and earn money through AdSense (this will cost you very little to set up, and earn you recurring income for a long time to come) or create an informational product based on any particular issue.

If you’re creating info-products for history-based niches, ensure that there is a lasting demand for your product. Current events and trends are a great barometer of what history the public is interested in. While there are always mainstay items like famous authors and artists, topical history niches such as the Napoleonic Wars may not generate that much interest (although you can possibly move laterally to selling war memorablia, and use public domain information as content to attract visitors through search engine).