When you buy a web hosting server with the purpose to start your own hosting company and to resell plans to various people, you may also need to sell domains, to give your clients the option to get everything they need for their new site from a single place. To be a licensed registrar involves thousands of dollars and a lot of documentation, so the most convenient solution is to sign up for a domain name reseller account with a current registrar company. Your reseller website will be connected to that account through the registrar's API. Using this kind of account has lots of pros - your customers will be able to acquire and to control new domains with ease; the price of a brand new registration will be lower as compared to what you'd have to pay as an end customer; also you'll be able to start reselling right away. The registrar companies that sell domain reseller accounts usually require a certain amount of money as a deposit.