Roofs maintain the integrity of the rest of the house and should be maintained as such.The price in which you purchase the property should factor in the age of the major mechanics along with windows, roofs, and siding considering where they recommend in their life cycle. 

Depends on where you are in your investment life cycle- i.e.

Liz has overseen over 1,500 units concurrently in 15 different developments all at various stages in the projects life cycle

You may find a few that are still good.....you may not - but you know that when you start.A lot of tapes reach the end of their life-cycle in small pools on the flip-market.

It's inconvenient, but it's just our biological life cycle, and it has to be accepted for what it is.

They can manage your whole PM lifecycle from website, prospect applications, screening, leases, maintenance, electronic rent collection, and all accounting.

(Ex: I would like to replace the old plumbing with PEX, I would like to add a bed/bath in the attic of the upper unit and water heaters and boiler are on the older end of their life cycle.)  

Investors often focus on returns but more important is where the investor is in their investing and also age in years life cycle.

Al of these have a normal lifecycle, and if you are purchasing a place that is on year 1 for all of these lifecycles you're probably safe having a few months of operating expenses in an emergency fund. 

Something that would benefit the data geeks would be to identify the inefficiencies within a given market through the lifecycle of real estate.