Moving career site to new URL from main site. Will it hurt SEO for main page?

[rflores]

For one of our clients we are building a career site and putting it under a different URL and hosting service (mainly due to security concerns of hosting it under the same host and domain).

almost 100% of the incoming traffic to their current career section (which it is in a sub-folder) receives traffic for branded keywords (brand + job/career/employment), that is, there are no job position specific keywords.

The client is now worried that after moving the site, the inbound traffic to the main site will be severely affected as well as the SERP results.

My questions are, will the non-career related SERPs be affected? I don't see how will they be but I could be wrong

If no, how could we reassure her that the SEO to the main site wont be affected? are there any case studies of a similar case (splitting part of the website under a new URL and hosting service?)

Thank you for your help.

PS: this is my first post so please forgive me if this has been asked before. I could not find a good response.

[hecklerponics]

Anytime a website URL changes there is a large potential for harm.  I would say that you can expect a significant drop in the near future after moving the site.

Make sure the old URL has a permanent redirect 301.  This tells Google (and others) that the website has been moved and it is a permanent move.  SERPs won't update immediately, so this will help you funnel traffic to your new website address.

In a perfect world, black-hats don't take expired domains with high DA and try to recreate the content to build up their affiliate marketing link strategies, but that's another topic.