Lots of opportunities to stop and prevent it. 

That will bring odors and accidents.

Reach out to agencies in your area (housing commission, Saint Vincent DePaul, etc.) explain the situation and ask them who provides eviction prevention assistance to renters.

Reason being for it is that insurance companies are getting tighter and tighter, and having a claim on your home can prevent you from getting further policies in the future and subject to much higher rates. 

Seller is free to tell his broker to limit inquiries to qualified (screened) buyers, as I mentioned above -- you assume that buyer with their own agents are qualified (pre-screened), but that doesn't prevent you from screening a buyer without a broker and IF he qualifies, have his sign a no agency agreement.So no, there is no "all/random" persons of inquiry.

I don't know if today's climate of the city recognizing a need for more housing might make some sort of small difference (something you'd have to discuss with them) but, other than that, this is an accident waiting to happen.

It is your responsibility to change the air filter to prevent this from occurring (see Lease, page 3, paragraph 2). 

If you mix funds, then any lawyer for a plaintiff -- say someone who has an accident on your property -- can "pierce the veil" of the LLC and show that all your assets, not just that one property, should be up for grabs.Cheers.

Forming an LLC in a specific state believing you will be better protected is not true and will not prevent claims from arising.Understand insurance and make sure you have the appropriate types of insurance depending on the investment opportunity you are pursuing whether it be land, a construction project, a tenant occupied property etc..

Who was I to stand in their way and try to prevent them leaving or enforce the terms of the lease?