For example the contractor had to replace roof or do other repairs to make the property rentable and I spent 2 hours talking to the roofing company and plumber? 

And/or assume that everything is trashed and you have to rehab the entire house.I have bought houses without going inside, but you can usually get on the property and look in some windows. check the roof, exterior siding, main panel, etc and get a pretty good idea of what the house will need.

This section will delve into the growing demand for green buildings, the benefits of sustainable development, and how these trends are influencing market values and investment decisions.Green Building Technologies: Innovations Shaping the FutureFrom solar panels and green roofs to smart building technologies and zero-energy designs, the innovations in green building technologies are endless.

They are cheap and will save you from future leaks and clogs.

A property owner may need a roof on their house they can't afford.

Multiple rental apartments under one roof are provided by multifamily buildings, such as duplexes, triplexes, or fourplexes.

Roofs never start leaking on flat areas, its always penetration points or valleys.

I agree with Ken, get some costs and see if it's worth it but depending on how old the roofs are on your dwellings if you have a claim and replace the roof your rating might not really change. 

I would focus for a listing price > $600k so you have more "space" for higher price.Also that 80k I'm considering the roof is fine.

If the resident has issues with the quality of the housing such as a failing roof or HVAC issue we would advocate strongly on their behalf as well.