Installing an alarm system in a 2 story duplex

[Richard Gaskins]

Hello everyone

I'm going to try to keep this simple. I recently purchased a duplex. It's 2 stories, 1 apt up and 1 apt down. The lower apartment has 2 access points, the front door and the interior side door. There is an exterior side door that leads to the stairway. You can access the lower unit's interior side door from the stairway. The upper apartment has 1 access point that can only be accessed from the exterior side door. 

Is there a way to install alarms in both units that can both deactivate the sensor on the exterior side door. I've talked to ADT. Sighs.... that's been interesting. I'm posing this question to current landlords who may currently have a similar configuration.

Thank you in advance for your assistance.