Reach out if I can help, or you can find more investing insights, methodology, and processes in my (free) weekly blog: ericfernwood.substack.com...Eric

But then I dug into their methodology. 

I do understand that rental properties are a function of appreciation but wish to know what would be the best methodology to understand the overall negative cashflow to asset appreciation ratio or a metric to benchmark it against e.g. % appreciation YoY.

I would only ever recommend Guesty if you're a large PM using Trust Accounting methodology. 

I looked it over briefly, but it seems to be pretty detailed on their methodology and includes really helpful tips in the front pages.

As much value as I see in your overall logic and methodology, that still doesn't address the central question of what home warranties are providing by way of coverage.

Calculating your income requires proper methodology, knowledge of guidelines, and often a worksheet to help with the calculations. 

Unrelated to investing per se but relative to fundamentally addressing the real world practices of effecient infrastructure in residential buildings as a whole is the extreme and profound unwillingness of individual property owners to actually embrace and implement equipment & methodologies to mitigate the "purported" climate crisis.From my myopic perspective having to fight with residential customers who have zero knowledge of thermo dynamic, ohm's law and efficiency measures is highly hypocritical.People claim to care but are closed minded to energy saving and efficient operating homes.End rant