We migrated to a more efficient HVAC system as part of the retrofit, but actually ran of the older system during the course of the retrofit.Other similar houses in the neighbourhood have average annual energy consumption 80 - 120% greater than this house.We just acquired another near identical house one block away and I am presently modelling a retrofit plan that, once finished, should see the average annual energy consumption be in the range of 30 - 50kW/m^2.  

I can't offer personal expertise on a specific contract, but when I have purchase/contract specific questions I've found the best resources are my real estate agent and attorney. 

Taking your grandfathers understanding and gut instinct on what a good property is and a good model to determine return on investment and you will have a competitive advantage over many other real estate investors.

Late model, shinny, clean, no big dents or missing headlight, is fine.    

The key to commercial analysis is modeling the current and future (potential) leases.

I'm considering training a VA with a background in real estate and finance to underwrite deals for me (or at least fill out the majority of the financial model).

While I think that's a business model people have played with (selling "turn key" STRs with bookings and everything), it's certainly not common and in your case, I wouldn't pay a dime for them.  

@Jim K. thanks for the thoughtful answer. i'm with you most of the way. your model seems based primarily on cash flow, except for where you say "reassess this number every five years based on the performance of the property and the amount of debt left..." how is debt/equity factoring into your model?

Maybe, but I don’t see enough turnover on deals to turn that into a sustainable model.

It's stressful, and the pricing model is the most overlooked piece (coming from a guy who made all these mistakes, trust me).