Regarding roaches, provided that the property is vacant, there is much success using Boric Acid.

It was thousands of dollars of damage as the carpets were saturated with cat urine and a feces stains, which progressively consisted of more bile and stomach acid, as the cat slowly starved.

Single family "decent" blue collar neighborhoods, the 1% rule applies very oftenThat being said, these "rules" are REALLY only guidelines or acid tests to quickly see if a property is "in the ballpark" 

It will still cash flow nicely becuase tenants will pay own heat afterward, but still, the 50% rule is a quick "acid test".

Solar hot water systems (popular in the Carter administration), used large, usually tilted up panels on the roof to preheat hot water or glycol in order to lower the homes electricity and/or gas consumption and to heat hot water.

I was going to hire a pro to acid wash it that way none of the detail is lost since this is sand stone from Scotland and I could give all the history and the cost of this place was crazy.

But it also gives leeway to the honest people to do what is needed to do the job right without throwing out the baby with the bath water.BTW, you do know that the "Chinese Drywall" problem encompasses several brands, and that the amount of sulfuric acid off-gassing varies not only by brand, but vintage.

I'm trying not to use muriatic acid if I can avoid it.

Cleaning with acid and leaving it on, especially over application, can cause similar problems over time. 

A loan constant is much like the acid test in measuring debt coverage, while it can imply performance it is not at all like the earnings per share for example.