pmpro_checkout_after_level_cost.php

<?php

/**
 * Adds text after the level cost text.
 * Add this code below to your PMPro Customizations Plugin - https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */
function add_text_before_submit() {
	echo 'Add additional text here';
}
add_action( 'pmpro_checkout_after_level_cost', 'add_text_before_submit' );