Insurance companies know the average life cycle of a building and if stuff is original or patched over time they know massive claims are a high probability in the future hence the really high annual quote.

Take a look at this thread, where we wrote about the lifecycle of a development deal, this may be valuable for you: https://www.biggerpockets.com/forums/44/topics/427144-lifecycle-of-a-ca-multi-family-development-dealFinally, we are an offer of help, our company provides real estate development consulting, and we can absolutely help you with your process. 

I'd recommend checking out this one: https://www.udemy.com/become-a-real-estate-investor-learn-the-fundamentals/ It has a lot to help get you started out with finding seed capital, finding a business partner, renovations, and the full REI lifecycle.

Perhaps the owner pulled the money out into different directions but the end result is a dumpy place that doesn't have anywhere to go.That's an asset class at the end of its lifecycle. 

From the home inspection we've come to find out that the HVAC, water heater and probably the roof are all near their end of life cycle.

I am in my research phase of my REI investment and I know I must understand the deal and cash flow analysis.But I have the questions regarding what is the life cycle should I think about?

Inventory is lower than average for the Austin area with a likely increase in the next month or so due the typical real-estate lifecycle here. 

However, the house is 15 years old, and the HVAC/Roof/big ticket items are nearing the end of their lifecycle.

Big ticket items should of cycled thru one lifecycle but coming to the end of the next one.  

Do a quick google search for "building life cycle span" and play around with the wording too.