There are different platforms offering domain names. You just have to know which purpose you want to serve in getting your own domain and if it is going to be a long-term or short-term use. One-time Purchased domains are bought in just one transaction. You will have the rights over your chosen domain basically, for all eternity. No renewals, no expiration dates. However this is much more costly than Renting. Getting a domain under a platform that offers this type of purchase will give you the freedom when to stop associating your identity to a domain and give it back to the parent. It is much more cheaper than one-time purchase since you pay annually and you get to decide if you still want to continue with your domain by renewing it the next year.