Its about the best practices we need to look.
We need to ask a developer few questions before we hire him. Just go to google write down there WordPress best practices. Come back and ask them about that. If they can answer hired them.
1. In WordPress, you must configure which domain should be used by your website using a site_url() and home_url(). While WordPress has a wp-config.php file where you can hardcode your website’s URL, it is way easier to use the native way. In your WordPress Admin Dashboard (/wp-admin/) you can navigate to Settings > General and edit your WordPress Address (URL) and Site Address (URL) fields. These fields should match, and should begin with http:// or https://.
2. use a child theme.