Tradespeople can hire too — every tradesperson account includes the client role automatically, so you can switch which one you're using at any time from the account menu (your avatar). (Signed up as a client and want to offer services? Apply to become a verified tradesperson from your account.)
Switching changes what you see — the client view shows hiring tools (search, post a job, your requests), and the tradesperson view shows work tools (browse jobs, your applications, payouts). Notifications and jobs stay tied to the right role.
If you open a link that belongs to the other role, Blue Seal switches you to it automatically so the page makes sense.