Set the setting to RFQ mode in setting 1 in general setting. Do not show prices. That will be the default.
Add the following to your functions.php
add_action('init', 'gpls_woo_rfq_check', 1000);
//check if the user should be able to see prices and purchase ( the normal WooCommerce setting)
gpls_woo_rfq_purchase_only(); // user can see prices and purchase normally
gpls_woo_rfq_purchase_or_quote();// user can see prices, purchase or request a quote