How to Setup a Pilot Site Parallel to Existing Site

[pypo]

Can anyone explain the right way to build a pilot site next to an existing public site. The domain names are the same. The goal is to build the pilot site, get client approval, and then switch over from the old site to the new site. Content from the new site will be different but the site domain name (URL) is the same.

I thought I would just create a whole new site at the hosting company, but my domain host doesn't let me create a domain with the same name in my account. There must be another way to go about it.

Thanks.