The website is physically setup as soon as payment is made. If you already have your own domain name, then you will need to alter the nameservers for that to point to our servers (we will advise you by email what they are). If you obtain a domain name from ourselves, we shall apply the nameservers for you.
Nameserver changes can take between 24/48 hours to propagate throughout the internet i.e. untill you can actually browse to your website in a web browser. However, in general it is a lot quicker than this and often pretty much instantaneous.