Best way to clone base site in multisite

So I start with a Perfect Base Site... OK?

Then I want to make that Perfect Base Site available to someone else...
http://www.perfectbasesite.com
http://www.perfectbasesite.com/somebody
http://www.perfectbasesite.com/someoneelse

Is there a way to Clone Perfect Base Site the way all the gazillion sites out their do it... when you become a consultant or a dealer for them?

They need their own Admin, Users and Posts... but all the rest of it all... can I start them out with a Perfect Base Site and let them run with it from there... on my Multisite install???

Which Theme or Plugin or combo creates this ability... I'm poking around and the answer seems to be "maybe" on a bunch of options...

Could you please come out and say:
"Use this theme & plugin or plugins"... for us new to WordPress junkies please?

Thanks in Advance!!!
Robert