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Thanks for the responses. Just to clarify, this isn't being done for SEO purposes. They want it this way so that each representative can have branded access to the site, and so that the content can be changed easily from one location (take for instance the listings, they change often).

As for the rel-canonical, it would be difficult to implement, because the sites do not exist. It is being redirected at the domain level.

I am working with a real estate client. They have one main site (ie. company.com) that contains all the info, then they have several name domains (ie. salesrepresentative.com) that are forwarding to the main site, but use domain masking to appear as if there is a separate site for each representative. My question is how can I make this legit in Google's eyes, or is this totally not advised?