It is important that you attempt to maximize the potential of each business you begin, but you should start by spreading your income base quickly by setting up four or five small online businesses and focus on expanding them later. Using public domain products, this approach is fairly easy and quite successful.
You can pick several public domain works, create a different product for each of them, and after you have set up individual websites for each product, return to improve and expand on each website. This will allow you to generate multiple income streams and then maximize the income potential of each stream within a short period of time.
So many people think of the public domain for starting a new business that they forget the most important aspect of using the public domain