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If we understand that a major portion of SEO is link building, I would say that url text (only) is not a link and does not offer any direct SEO value. If the url is to good content that you're trying to amplify, someone else could see it and re-post it in other places which would (in some cases) provide SEO value. Just my two cents...

Well they are not being closed because they are being fullfilled but becasue that is the period the client sets to receive CVs. They want more CVs but for that they need more SEO visibility and I thought black hat could work for a short lived link.

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.