You should be able to buy it from anyone who sells them - they are registration agents who act as a middle man between you and the registrar.

Once you have the domain name, you have to renew it, usually every two years, and the renewal may cost more than the original purchase. There's no way round that. You can also transfer it - you shouldn't be stuck with the registration agent you started with if you don't want to be.

You also need hosting - that's an ISP to handle your mail and host your web site using that domain. That ISP may or not also be the registration agent (they often try to get you to bundle both services with them but it's not essential).

Anahata