First of all, change the locks on your front door, back door if u have one, and the room u grow in. Try to get one that looks like the lock your land lord used, but not the same brand. If they ever say anything to you about not being able to get in your apt, youll know they tried to get in without you being there which is good...just act dumb and that it's their mistake and not your fault they dont have the right key. in the very least this will buy u time. if while u are there the guy notices something and calls u out..just offer him some money but know for sure that u have to end what youre doing because now someone who supposedly has exclusive access to your place knows what youre doing and may decide to rob you, not call the cops.
Now about getting around inspections. Most of the time the land lord will just change the filter on the AC and inspect the stove and smoke detector, as long as your grow isnt in any of the rooms these things are in you should be good, you can just put a lock on the door and be confident no one is going in there. but if they do need to get in that room, put a lock on the door anyway and make sure ua re there when they decide to do the inspection...when they ask to get into the locked room just say "oh that's so-and-so's room, they lock the door" and then offer to do what ever it is they were going to do. if they then insist on entering the room tell them theyll have to wait till so and so gets home from work or what ever...buying you time to get rid of what ever it is you dont want them to see.
just be smart about these things and plan it out way in advance cus this is seriously your life you are messing with....with the laws being what they are and people being natured the way they are...cops should be equally feared as thieves, so yes even a small plant can invite danger into your world