there, I am building a multisite similar to etzy.com.

Hi there,
I am building a multisite similar to etzy.com. Registration to etzy is like 3 steps but what I have now with multisite and buddypress seems like a whole afternoon process. I would like users to be given a site, mysite.com/username and a blog, mysite.com/username/blog automatically at registration and then direct them to their buddypress page without them having to decide for themselves for any of the above.

How I can I make this happen?

Please help.