One family finally moved out after a series of flooding incidents left them with health problems and a decaying house."

Maybe counteract it with, "if your complaint isn't a lease violation, you will owe the fine amount for wasting my freaking time!".

I'm not afraid of mobile homes at all In fact I kinda like them it's a shame that so many potentionally great homes are just sitting here decaying though 

Cash is a wonderful way to counteract risk.  

Well if her house is paid off the Grandma has "dead equity" meaning each year the money is not growing and is reduced by inflation but hopefully counteracted by appreciation so that she is at a neutral to positive position annually on her house.Some older people people that already have wealth do not want to take risk and prefer security.If he borrowed the money from her and a deal went bad she could lose a chunk of her net worth and destroy the family.Also she would still be left with the loan on her house.If she was to invest in anything and preserve wealth triple net or something similar with low risk would be better than rehabs.The only thing riskier than rehabs is ground up development.If she has a bunch of money she could lend some to rehabs and some to invest in other parts of RE.

To counter act that I chose a  property management company and it  was terrible, very uncommunicative, poor tenant selection,overcharges and poor care taking. 

Legal abandonment is different than a property merely being in a such a state of decay that it looks abandoned.Occupancy of an abandoned property is a type of Equitable interest in the property.   

Just sat there slightly decaying and has over 200 cyds of debris inside not including 3 cars in the garage with no tires on them. 

The place decays. 

It really is sad to see all those old building decaying.