functions.php

<?php

add_filter( 'init', 'guest_page');

function guest_page() {

    if ( is_single() || ( is_home() && !is_front_page() ) || ( is_page() && !is_front_page() ) ) {

        $_post    = get_queried_object();
        $_post_ID = $_post->ID;

        if ( !isset($_post_ID) )
            return;

        if ( !is_user_logged_in() && !empty(get_post_meta($_post_ID, 'guest_page', true))) )
            wp_die('No Access');

    }

}