Did someone install too small a system, did the Freon leak out, are the air filters dirty. 

The leak was coming into the kitchen and on top of the refrigerator. 

As for any oil tank, if they're leaking oil into the ground then yes you have an environmental issue to deal with. 

If you wait 30 years to start budgeting for a roof, the house will rot into the ground from leaks before you have accumulated enough to replace it.

It comes with the territory like a water leak, roof damage, etc..My $0.02 ...

I hired a private detective before that found an owner I was looking for and knocked on the door and made contact with them for me.

Prevent sewage leaking and destabilizing the foundation. 

Shortly after moving in, this house (built in 2006 so 18 yrs old) styarted having issues - cooktop working erratically, they replaced it with a high-end (GE Profile) new one.....Dishwasher started leaking, replaced with brand new GE Profile. 50 Gal water heater went out (elements) they replaced.So in just 6 months, they have spent about $5000 on me.

We closed a few deals but its very tough.. the skill set is that of a private detective.. and then being able to close the deals..

They brought in a "plumber", said the house had multiple leaks in the pipes, needed re-piping and concrete broken up to fix the second leak.