Where possible and practical you might want to use electric instead of gas to save some of the expense. 

He said he shut off his gas to save money in the summer.

If you have a simple design with all utilities on one side of the ADU, this will be cheaper than having to run drains, electrical, gas, to both sides.

I don’t know the difference in cost between the gas and electric in your state or if you had any plans to meter back the cost of the gas to tenants.

So they need the stove to be removed from the unit and the gas to be capped to not count it.

You have a unit without a heater, I have 2 units without a heater and one of those units is without a hot water heater (no gas to that unit - both the heater is out and the gas is off for unrelated item (a leak)). 

After fees, dumpsters, gas to drive cross country, etc..

The heat had to always be at least 68 degrees Fahrenheit half the year or tenants would call 311 and get me fined (gas to keep the house warm cost me $850/month because of the poor insulation).

Let's say you get a service call for no hot water when it gets checked out there's no gas to the hot water tank to light the pilot.

So Austin is hot and to add gas to the fire, we just took the #1 spot for best city to live in the US.