EA doesn't allow locked doors on community lots or additional homes. I had to find a mod for that. Seriously, who wants people wandering into your room while you're on holiday? Ewwww. I won't link the mod but I'll give you the name of it. Nona_LockCommunityDoor. Search that and you should find it. I mainly got it so I could lock the barn doors and gates on my additional property which is just for my horses. Saying that, can't burglars get past any locks? For them, I'd just have alarms.