If issues come up I could non renew at any time and this would give me greater leverage if things were to deteriorate further, it isn't like you are worried they will leave with no long term lease.  

These are some of the ways the clients could be affected by property managers who are not prepared: Extended VacanciesInadequate marketing strategies and tenant screening processes can result in prolonged vacancy periods, translating into substantial lost rental income.High tenant turnover due to poor resident relations further exacerbates vacancy losses.Inadequate Maintenance and RepairsNeglecting preventive maintenance and delaying necessary repairs can lead to accelerated property deterioration and higher long-term repair costs.This can also negatively impact tenant satisfaction, contributing to higher turnover rates.Legal and Compliance IssuesLack of knowledge or disregard for landlord-tenant laws and regulations can expose investors to costly legal disputes and penalties.Failure to properly handle security deposits, evictions, or fair housing practices can result in significant financial liabilities.Ineffective Financial ManagementInaccurate budgeting, expense tracking, and financial reporting can lead to uninformed decision-making and missed opportunities for cost savings.Failure to optimize tax strategies and leverage available deductions can further reduce net returns.Diminished Property ValueInadequate maintenance, high vacancy rates, and poor tenant screening can negatively impact a property’s perceived value and appreciation potential.This can significantly affect the long-term return on investment when it comes time to sell the asset.While a 10% management fee may seem reasonable for a well-performing property manager, the cumulative impact of mismanagement can quickly escalate the effective cost to investors, potentially outweighing any perceived savings on the management fee itself.

fix-it-all (joint compound with some additives) is not suitable for exterior at allYes it will wick in water as the paint deteriorates, and cause more rot, and keeping a good coat of paint on it won't be enough long-term in many/most climates.bondo (polyester auto body resin) is a cheap-ish "alternative", although harder to get detail work just right and not really all that suitable anyway (maybe ok with a good epoxy / primer, perhaps?).

You'll also want to ensure you have a good property manager to look after the upkeep of the property if you are not there to notice anything deteriorating or which may need attention.Creating an LLC in California could cost you a minimum tax of $800 every year.

One day he wrote an email about the mold and dust and claimed the taped up areas had come loose and the plastic was deteriorating.

Such a policy leads to property deterioration and stifled investment in housing."

I've met investors in D class who buy the property and don't bother to fix stuff, soon enough the property and the quality of tenants deteriorate. 

The bottom started deteriorating after 2 years but the rest has held up great.  

Also, could it be not that he don't care but he is mentally deteriorating?

All of these are expenses that you must cover as the owner, or deferred maintenance will build up and your property will deteriorate.