Shall i get such engine which is used for like bravenet site.

My need is to create a web site which is work
like a web site www.bravenet.com or
www.sampa.com. Which basically create a web
site for user and put it on server. So my
question is any engine is available which helps
me to give such facilities to create my web
site. I just don’t know from where to begin and
what to use for it.
Help me it’s urgent.
Thanks.