Landlord Is Pressing That I Am Moved Out By The Date Given On My Lease Termination - But He Already Sold The Place

Location: Massachusetts, I’ve been renting a unit in a 3 story apartment building for 5 years now. I’ve exhausted all my other free advice avenues, so I’ll be extremely grateful for any answers/advice anyone has for me…

Some context that might matter: My landlord lives below me, is 95 years old, and has made these past 5 years hell by letting himself in (or breaking in when the door was latched) at all hours because he thinks he hears water in the walls, the ceiling is dripping, water bill is high etc. He tries to break in to my bathroom while I or my roommate are in the shower (we’re 25F, BTW).

Last month he said he was going to have the plumber come up to look at our tub on “x” date- I asked him not to because no one would be home, I have a cat with heart disease that needs medicine twice a day and I was scared he would get scared and run off. Well, he did it anyways. Left me a nasty note that said the “plumber doesn’t work at your convenience”, and left the door WIDE OPEN. My cat was still there, thank God, just really scared and hiding under the bed. The place was filled with flies, bugs, a couple of wasps that could’ve stung the little guy… Saying I was pissed was an understatement. I called him and told him he left my door open, to which he said “oh, I didn’t realize. I had to look at the pipes I didn’t have a choice” and nothing else. I told him the next time he so much as yanks on my door handle without permission, I will sit down with his wife and adult children and let them know how concerning I find his behavior. He did it again. I called his oldest son. Son did not care.

His response? He’s selling the place. Gave me a notice to terminate dated for 11/01/2026, as reminds me frequently to be out by that date. I’ve added an extra lock to the door and installed security cameras.

Sorry that was so much, but I needed to set up for this question - If my landlord will no longer own the property by the date my lease is terminated, where does that leave me legally? If I stay an extra day, am I squatting in someone else’s home? Would the new buyer be dealing with me? The landlords son told me there was no need to communicate with the buyer and all communications should go through him until I leave, but the place will be sold just before then so I know that’s not true. They kept trying to telling me things I knew weren’t true and shutting down when I corrected them - like that I have to allow repairs on the landlords schedule, or that I had to leave as soon as I was given notice to quit, or that they can enter anytime to show the place to buyers etc.

I feel like I’m fighting a war I never prepared for, if anyone can help at all I would greatly appreciate it. The stress is killing me.

ETA- I AM NOT TRYING TO KEEP LIVING HERE LONG TERM. I know that unless there’s the miraculous scenario a buyer just wants to rent at the same price, I’m leaving. My issue is I’m getting constant messages, my landlord at my door making sure I’m packing up, etc. It was giving the impression he suffers a stark consequence if this place isn’t spotless as soon as my lease is up. I should have posted to [r/nostupidquestions](r/nostupidquestions) ????

2nd edit- I will suffer whatever consequence of double locking my door while I shower and to protect my cat. The lock stays. I’m not keeping him out of the unit. I just want to shower alone and keep my best friend alive.