The agent said his partner, also an agent, is living in it, so that the house is occupied to prevent vandalism.

If the air isn't circulating you can get all kinds of issues.

I don't know what kind of materials or product I need to finish this wall, and because of flooding how much time I should give it to air it out.

Think of it as preventative medicine.

There are pros and cons to both sides...Double-closing adds protection because it basically prevents the seller from finding out how much I am making on the deal.

Back then, it ran little over $60.00 month, except the summers where it is affected by air conditioning. 

Ordinary wear and tear shall not include any damage or deterioration that would have been prevented by good maintenance practice or by lessee performing all or its obligations under this Lease.

But there also was no title company that obtained an affidavit of title from the previous owner, previous owner could've owned a contiguous lot that was an issue, been prevented from selling your lot by deed restriction, or easement, there could have been fraud or forgery or someone that claimed to be the manager of a company or an executor of an estate...or how about if a seller sells to you and sells the same property to another buyer, he takes both of your money and too bad if you don't get recorded first (I actually handled a major litigation when I was clerking in law school about that.

Protect the rest of the interior by isolating the area and using a negative air blower to suck out the spores.

Definitely get landlord accounts if you can to prevent service from being shut off between tenants.