check_user_valid_cron_hook

add_action( 'check_user_valid_cron_hook', 'check_user_valid_func' );

if ( ! wp_next_scheduled( 'check_user_valid_cron_hook' ) ) {
    wp_schedule_event( time(), 'daily', 'check_user_valid_cron_hook' );
}

  function check_user_valid_func() {

     // The Query
    $user_query = new WP_User_Query( array( 'role' => 'Purchaser', 'fields' => 'all' ) );
    $today = date("U");

     // User Loop
    if ( ! empty( $user_query->get_results() ) ) {
        foreach ( $user_query->get_results() as $user ) {

            $validuntil = types_render_usermeta( "date-of-home-purchase", array( "user_id" => "$user->ID", "output" => "raw" ) );
            $user_id = $user->ID;

            if($validuntil < $today) {

                $user = get_userdata( $user_id );
                    $user->user_email;

                    $message = '
<html>
<head>
<title>Email title</title>
</head>
<body>
<p>Some text</p>
</body>
</html>
';
                    wp_mail( $user, 'Your subject', $message, $headers, $attachments );

            }
        }
    }
}