Move Beta Site Build Location so we can implement Launch Roach

Here is the Issue:

We have a an online magazine, wordpress based site we are building at the domain www.example.com

We have now decided to continue building the site away from www.example.com and instead point Launch Rock to this domain so that people interested in the magazine can sign up for interest.

Therefore we need somewhere else to build the Beta site. I assume this would be a sub domain somewhere. (your the expert tell us)

Job/Task
We need someone to move all files from www.example.com to the new location.
We will need to be able to login to the Wordpress backened easily and continue building the site while seeing changes etc.

We will then point Launch Rock to www.example.com

Please get in touch with how you would do this and timescale.