@Vicki Dungan - I would say yes you should remove it. That is a pretty big invasion of privacy. Outside of that, I would personally never rent a property where there is a camera inside, even if the owner said: "it doesn't work or is turned off". I would want it removed.
Wow. That's creepy. Do you work for the government? In most states, an undisclosed audio or video device placed in the interior (non-common) of a private residence would be illegal and could also result in a civil lawsuit against the landlord.
Be sure to check with an attorney before you do this, and maybe your conscience.
You absolutely cannot leave a working camera on the interior of a tenants home. This is felonious, unnecessary, and tyrannical. I assume you don't allow your mortgage broker to leave a camera in your house?
Treat your tenants with the utmost of respect.