A few companies have offered low-cost, below-cost or even free domain registration with a variety of models adopted to recoup the costs to the provider. These usually require that domains be hosted on their website within a framework or portal that includes advertising wrapped around the domain holder's content, revenue from which allows the provider to recoup the costs. Domain registrations were free of charge when the DNS was new. A domain holder may provide infinite number of subdomains in their domain. For example, the owner of example.org could provide subdomains such as foo.example.org and foo.bar.example.org to interested parties.
Fiverr is one of the biggest providers in the gig economy on the web and you can sell a wide variety of services and products through this medium. Do the research and find out what you can offer. However, keep in mind that like any other money-making task, it takes time to succeed here. And stellar reviews will help you generate more and more income over time.