Firearms in apartment - Building Inspector Wants To Come By - Am I Legal

I got a knock at the door today and looked out my peephole to see a mexican lady standing outside my door. She was accompanied by a tall bald headed guy. I figured she would leave after knocking three times but she just stood on my landing and knocked on the neighbors door as well. I didn't open it and decided to call the front office to ask if this is someone they send. Front office said no they might be solicitors.

Well about 20 minutes went by and I got in my car to go get some dinner. On the way out I see the mexican girl in a golf cart next to a car that the bald headed guy is getting in. So I asked if that was her knocking on my door. I told her I thought she was selling candy bars or something so I didnt open the door. So the other guy says he's a building inspector then he joked that he will come by tomorrow at 7:15 am and asked why I didn't open my door. I told him that I didn't know them etc and he said why do I look like a scary guy. He says don't worry she has the keys to the apartments if you aren't home.

I plan to call the front office tomorrow because they said they will leave notices on doors if they plan on entering your apartment. The only time this happens is when the bug guy comes around to spray. I was locked and loaded if she had put a key in my door they would have had some explaining to do.

Maybe they are looking for drugs or something but if the Building Inspector guy sees my shotgun propped up in the corner is it legal to have even if I bought it at a sporting goods store and haven't registered it?

I don't really like the idea of this guy coming in my apartment without my notice. My dogs would bite him probably and I might be startled into shooting first.