Age-old question I guess.
Hire someone who, you think, and can understand, is a good fit for you according to their portfolio and past activity. To this day, tracking someone is not that tough. Simply follow them for some days in their social network, and you can sum up something. Even you can [sometimes] verify their portfolio images using google’s image search using an image. (I’m suggesting these to someone who is desperate ☺️)
Take a backup of all your things before taking a developer or an active development in. cPanel grants FTP access; make a FTP access only for your developer, and it can even be restricted to specific subdomain or add-on domain.
If they destroy your site, revoke their access and deploy your site from backup. If they somehow spoil your cPanel access, contact to the vendor and get your access back by resetting password. (Still, I’m suggesting these to someone who is desperate ☺️)
As you said in comment:
I’m looking for someone to be in charge of the site, planning and posting articles etc., not just setting it up.
WordPress has lesser privilege user accounts, create one with contributor or author privilege and give them the account to do some site follow up and article posting etc.
And controlling privileges for them time-by-time is very handy using plugin like this User Role Editor or Members.
But always, do trust someone who is trust-worthy. I found trust is everything. Pick someone; not just Hire one.