As a freelance webmaster for websites run by WordPress, I do sysadmin, development and support stuff like:
- Keep WordPress, themes and plugins up to date
- Backup all files daily as part of my default maintenance service. Or design an individual backup strategy for you.
- Secure your website according to your needs
- Optimize the performance
- Analyze all technical aspects of your SEO strategy
- Offer IT-Support to you or your customers