They seem to require ongoing routine maintenance (water/chemicals) and start to need repairs as they age.

The tenant is responsible for opening/closing and chemicals to maintain the pool.  

Buyer is a smart guy....chemical engineer...but just not dealing with these kinds of things every day like I am.....so there is the value of your great agent.   

I am more concerned about actual chemical contamination or criminals who lived in the house that a parent owned showing up after they get out of jail.  

Older homes especially have a lot of chemicals/dust/asbestos/lead in them - this is not good to breathe in for you or your family. 

Washes will likely need an environmental survey that can be complex. a great person to connect with would be a chemical supplier.

Any cement previously drilled through where a termite company injected their chemical and patched the concrete?

Even if the grout is sealed, the tenants do not care enough to clean the mess in a timely manner, the stuff in it will stain the grout and with the chemicals and pressure wash the seal will fade/go away.  

There is always someone who will dump chemicals all over the place and call it a treatment, sometimes this works.

If you get out towards Pasadena area, it’s all oil refineries and chemical plants.