When you come to register a new domain name, you have to register it for at least one year, and this will cost about $10-$12 or slightly more.
You will have the option of registering for multiple years: 2, 3, 5 or even 10 years. Should you do this?
There are a few advantages to registering for multiple years. One is that you will often get a discount on the overall yearly price if you do this, so if you plan to keep the domain as an investment, or to build a permanent web site and put a lot of work and promotion into it, it is a good idea to register for multiple years.
Another advantage is possibly to do with how the search engines see sites which are registered well into the future: they view them more favorably, and are likely to give them higher rankings in the results pages. At least, this is what many Search Engine Optimization companies believe. No search engine releases the details of their ranking algorithms of course, so this is really guesswork.