Need help finding a way in

I would say just make sure to check all the doors and when its safe climb to the roof to check there as well

Maybe wait for nighttime if you’re going on the roof, and one of you be a lookout while the other one checks. Keep in mind I’ve never explored at night.

Do the doors have locks that's also use keys?

Depends on the door: Deadlatches - spring loaded that automatically lock when closed, could use a hook and pick set from your local hardwares store and loid the latch. Deadbolt - if you're good with lockpicks, schlage and kwikset are pretty low tolerance, use a rake pick. If the door opens inwards (which it shouldn't because of fire codes) you could stick a rigid piece of plastic through the door and jimmy the latch out of the way. Most electronic access controls will have a motion detector above the door to unlock it, get a can of computer duster, turn it upside down, and spray near the sensor. from my experience, most installers DO NOT wire "door forced" sensors to the main unit so this shouldn't be a problem, but that's most installers, not all. My last piece of advice: check near the doors for a keypad, chances are that's a security alarm, if you see a red light on a keypad - it's armed and you should not enter. If you do, chances are you could also trip a motion detector and trigger the "cross zone" which is an automatic burglary verification, and law enforcement will be notified immediately. if you can see through doors with windows, look for a little block on the door and frame, this is a magnetic reed sensor.