You can scope the chimney from the top and see if the current liner has deteriorated or isn't safe to use (evidence of pervious chimney fires, cracked/pitted/missing tile or exposed grout, etc) This should run around $4k all in (including removal of tile liner), unless this is an extremely odd shape or size. 

if the vent starts deteriorating this can happen with partial blockages.

Due to my uncles deteriorating condition, he didnt keep up the properties too much, so all of them are vacant.

We removed a deteriorated concrete pad which was actually a planting bed that someone had filled in.

I believe with new services provided commissions will be deteriorating.

It will be interesting now what happens to all those 5+3s in the suburbs...is the market deteriorating for those?

Consequently, one market has deteriorating cash-flow and another has awesome cash-flow.  

At first glance with its deteriorating look the investment was unreliable, but after in-depth analysis we began to see possible opportunities.

The current onwer must have cash-flowed the crap out of them and let them deteriorate into nothingness.

You may not with the sagging areas as they may be deteriorated.