I've been debating whether or not I should acquire a backlink from the sub-domain of a well-established edu site. The main domain has millions of backlinks, high TF, CF, and DA. However, the sub-domain has no backlinks and the TF and CF are 0 but the DA is exactly the same as the main domain. Would it be valuable to acquire a backlink from the sub-domain of this site? Or will it be a waste of time and money? Please let me know your thoughts on this?