I'd say I have a 50/50 chance of sub-metering (which would be the ultimate win), but if not I'm feeling confident I can still make a huge dent in the bill with low-flow toilets and a comprehensive plumbing inspection. 

According to this website the average household bill for water in CA is $65 which would be $260 for a fourplex.https://worldpopulationreview....

However, I can assist with info that is a bit more comprehensive than what is on airdna if you're looking to purchase.   

We focus on commercial multi-family properties that have a target rent of 30% of the median household income or less.

@Michael Plaks very comprehensive.

I plan to write a comprehensive review after I am done so stay tuned... 

I look at $/sq ft of the property at purchase, and for rent, then median household income of the census tract.Every property is good deal if there is a market to rent to.

A BOP is a more comprehensive policy with a few bells and whistles on it. 

It includes, among other things, a comprehensive map of the Cleveland area, grading each tract from A+ down to F, with a consistent, objective and transparent methodology using publicly available data rather than a broad-brush subjective approach.

They are, however, not accustomed to running a household and are likely to be very gleeful about being on their own, unsupervised, and far from parental eyes.