Matt, I guess that for a gas stove even without turning on, a leakage of large amount of gas can cause a problem, even an explosion.

This cause water to leak out of the connections and causes water damage to the ceiling.The washer/dryer is in the hall upstairs on our units.We have also found tenants will use the cheap rubber hoses instead of the steel braided ones or not have a washer fitting inside the connection which causes a leak.Also if it is an older washer or connections at the wall the threading is older and even if you tighten it will leak.This is why we use Teflon tape when putting the steel lines on.It fills the imperfections of the threading and stops any leaks at the connection.Another area of leakage is at the discharge hose.If it is not properly clamped at the washer,has an old hose,or where the discharge hose goes into the drain line could cause a leak.

I imagine that's due to roof damage and leakage. 

If you have poor management, you will have cash flow leakage.   

These include defective construction, excessive dampness, leakage, decay, termite damage and continuing settlement. 

After we purchased the property, there has been water leakage and part of the ceiling came undone as well as the AC stopped working.  

You should be able to identify the 'leakage'. 

The warranty company denied our claim because they said corrosion in the coil caused leakage which isn’t covered.

They disclosed the water leakage.

I've had a leakage problem with one of my duplex units for quite some time now; even after fairly extensive drainage landscaping, the problem is still occurring.Thanks!