To display lettings fees you'll need to override your single-property/price.php template and add the link accordingly. In the example below we're opening the fees in a lightbox but you could also link to a separate page.
Step 1 - Override single-property/price.php
You'll need to override this template so as to not lose your changes when you update in the future. You'll need to copy:
/wp-content/plugins/propertyhive/templates/single-property/price.php
To:
/wp-content/themes/{your-theme-name}/propertyhive/single-property/price.php
Step 2 - Add lettings fees link
Within this price.php template then add the following where you would like the link to appear:
if ($property->department == 'residential-lettings') { echo ' <span class="fees-apply-link"><a data-fancybox data-src="#lettings_fees_lightbox" href="javascript:;">' . __('Fees Apply', 'propertyhive') . '</a></span>'; echo '<div id="lettings_fees_lightbox" style="display:none; max-width:400px"> <h2>' . __('Fees Apply', 'propertyhive') . '</h2> ' . nl2br(get_option('propertyhive_lettings_fees')) . ' </div>'; }