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Multitenancy in mezzanine is done via domain names. You will need to run http://dev.site and http://esdev.site or similar in development (add the entries to your hosts file and make sure they match the listings in the sites part of admin).
In production you’ll also want to use two different domains too.
For example, my personal site http://dpn.name/ and my business site http://behest.com.au/ are both running off the same mezzanine install.
Later on when you have the right setup, you’ll be able to add new posts and pages to each specific site by either logging into the admin via each domain name, or changing the currently active site in the admin (the drop down is in the top right if you have multiple sites set up)
Hope that helps, please let me know if you need more info.