They know the tenant base, median rents of different areas, how much to increase rent each year, ranges of repair costs (ex: tenant calls and says AC isn't working, no hot water, faucet is leaking, the HVAC system goes out).

Your standards can be even tighter based on bedroom size, flexible space, plumbing capacity, and other factors.Check out the Keating Memo from HUD to learn more: https://www.hud.gov/sites/documents/DOC_7780.PDF

Why do you have a standard if you don't intend to adhere to it?

Sure, the fill time can be almost non-existent, but you also may need to abide to standards accepted by the previous property owner.

To manage this, find the average electricity, water, and gas usage in your area.

Definitely wouldn’t do a standard 3/3!  

Maybe find out you didn't replace cathodes, and the water is harder there.

I wasn't sure if there was an "industry-standard" way to approach investors, luxury brokerages, etc. 

You should be calculating Cap Ex for all long term items that will need replacement at some point - appliances, roofs, ac, water heater, etc.

The standard is your intent and  how you can demonstrate the intent of the property.