I have a property that I paid $140k for and had a water line leak issue that cost me, it wasn't tenant caused but still will dent my returns.

How will you know if there's a water leak when you can't see the floor, walls, or ceiling?

Never seen any talk or research on this, but seems like kids might do better in school if the school is newer and in good repair and things work vs those that leak and fight temperature control and other issues.

You may want to look into that coverage in case the Septic tanks leak. 

Roof age and condition: Create a visual checklist to use during a showing for signs of moisture intrusion or past/active leaks and make every attempt to gain access to attic/roof sheathing.

Most times the water usage drop is significant and the residents are much more likely to notify you when they have a leaking toilet etc.We've also found that the expenses for the material and install is often recovered within two years or less.Sometimes we need to reduce the rent by $20-30 less than what we would otherwise be able to rent it for, but in some cases, it doesn’t affect the rent at all.

If you find a minor leak, or the appliances are on the older side, you can stipulate you won't make them pay for it. 

Quote from @Ryan Leake: @Darius Ogloza is very experienced in Marin County and may be able to offer some guidance! 

If it leaked into subfloors, then you may have to tackle some of those.  

I recently discovered a leak in the basement coming from my 1st floor toilet.