See snippets comments for the form’s hidden fields

/*
 * 2 forms:
 * one that goes to the listing owner email for paid listings,
 * the other goes to the site admin, for free listings.
 * 
 * All forms must have a hidden field labelled 'package_type',
 * with default value set to 'free' & 'paid', respectivelly
 * Both forms are added to the single template, and the filter hides or shows either.
 */

add_filter( 'geodir_show_ninja_form_widget', 'gd_support_maybe_show_ninja', 999, 3 );

function gd_support_maybe_show_ninja( $show, $post, $args ) {
    if ( ! $post instanceof WP_Post || ! class_exists( 'GeoDir_Pricing_Package' ) || ! function_exists( 'Ninja_Forms' ) ) {
        return $show;
    }
    $form_id = empty( $args['form_id'] ) ? false : $args['form_id'];
    if ( ! $form_id ) return $show;

    $fields = Ninja_Forms()->form( $form_id )->get_fields();
    if ( empty( $fields ) || ! is_array( $fields ) ) return $show;

    $form_package = false;
    foreach ( $fields as $field ) {
        $settings = $field->get_settings();
        if ( empty( $settings['type'] ) || empty( $settings['label'] ) || empty( $settings['default'] ) ) {
            continue;
        }
        if ( 'hidden' === $settings['type'] && 'package_type' === $settings['label'] ) {
            $form_package = $settings['default'];
            break;
        }
    }

    if ( ! $form_package ) return $show;

    $package_id         = geodir_get_post_package_id( $post->ID, $post->post_type );
    $package            = GeoDir_Pricing_Package::get_instance( $package_id );
    if ( ! $package ) return $show;
    $package_is_free    = ! intval( $package->amount ) ? true : false;

    switch( $form_package ) {
        case 'free':
            return $package_is_free ? true : false;
        case 'paid':
            return $package_is_free ? false : true;
        default:
            return $show;

    }
}