You need to have a talk with them and either set them straight or send them packing.

Now that time has passed and everyone has settled down from the new management shock they are no longer afraid of you and thinking about packing their bags.

He told us he can't move until Octoberish, and we did notice him packing his stuff up, but here's the deal1.

We tried to stay overnight while we were cleaning initially, and ended up getting a hotel instead as our lungs felt like we smoked 2 packs of cigarettes after several hours in the home, even though the lady had quit smoking months before.  

Throughout this month they have refused to leave the house for any showings and on a few occasions have told us that a showing request wasn't convenient for them as they are packing and moving.  

He agrees and begins to pack up and move out.

I am 100% month to month, and tell all tenants up front and in no uncertain terms that I use month to month so they can leave anytime they want and I can send them packing any time I want.

The humidity thing can be a concern, but only if they've got the place packed with plants.

Apartment association's recommendation for specific area - every time I'm at Staples buying office supplies and see people buying the pack of carping copy staples brand lease forms I cringe.

That said, I don't think 18 people are allowed to pack into a studio apartment.