Delete old users files on a secondhand Mac
You don't own any of the software on it &amp; will not be able to update it.
You don't even own the OS &amp; will not be able to update that either.
At some point, something will ask for the credentials of the original owner... &amp; you won't know them.

Apple's policy is opposite to that of Microsoft. With Windows the OS &amp; apps belong to the machine &amp; changing the machine's owner is simple. With Apple, everything belongs to the original purchaser - tied to their Apple ID, &amp; they can change machine, taking their purchases with them. They can't, however, give that software away, it is irrevocably tied to the original Apple ID. This includes the OS itself.

Your best course of action is to completely wipe the machine &amp; start over.
As a new owner of a blank second-hand Mac, the new OS you install will now belong to you.

What to do before selling or giving away your Mac should already have been done by the previous owners - &amp; frankly for a company to not wipe its old machines is really unsafe; who knows what sensitive information is still on there... or what spyware, viruses etc...

Start from Step 5 on that page &amp; completely erase &amp; reinstall the OS.