For example, someone wants to invest $5 million but wants special treatment in recognition of an unusually large investment.  

The property will qualify for 1031 Exchange treatment as long as it has been held for rental, investment or business use. 

She sent me a vague, hard-to-see photo of the eggs, but I took her word for it and sent a pest treatment guy there to treat the eggs and spray around the property.

Does anyone know if that is sufficient to receive that tax treatment?

I have now been informed that they have found more tumors, and additional treatments will be necessary.  

You/she has not considered (or apparently does not understand) De Minimus Safe Harbor rules or the concept of In Service date for the proper treatment of remodeling expenses.  

When you repair (as opposed to replace) things, you get better tax treatment.

I do know pest control treatments fall under the guidelines here in KY which has been useful to me for unit inspection b/c my buddy owns a pest control company, just saying.I don't believe I would state the unit is inhabitable to the housing commission b/c they might hold you responsible for her temporary re-location until its repaired.

See below for treatment of payments due under a federal income tax installment agreement.When a borrower is obligated on a mortgage debt - but is not the party who is actually repaying the debt - the lender may exclude the full monthly housing expense (PITIA) from the borrower’s recurring monthly obligations ifthe party making the payments is obligated on the mortgage debt,there are no delinquencies in the most recent 12 months, andthe borrower is not using rental income from the applicable property to qualify.In order to exclude non-mortgage or mortgage debts from the borrower’s DTI ratio, the lender must obtain the most recent 12 months' canceled checks (or bank statements) from the other party making the payments that document a 12-month payment history with no delinquent payments.When a borrower is obligated on a mortgage debt, regardless of whether or not the other party is making the monthly mortgage payments, the referenced property must be included in the count of financed properties (if applicable per B2-2-03, Multiple Financed Properties for the Same Borrower. 

However I still very much like Vegas for some of the best if not best tax treatment all around in the US  and desert conditions IE no snow or hard freeze generally no soil issues  massive thunderstorms that ruin roofs etc etc.