If you have the persons information to run the background check then you could check the persons background without their permission or knowledge.
The person would not have any knowledge of you performing the background check unless you or someone told the person.
However landlords are required to tell the person that they're checking their background and will need some information from the person anyway.
But if you have all the persons information you could run a background check on the person online and they would not know about it.