This will allow you to ride the wave of market fluctuation.

Mold is a function of humidity not temperature fluctuation.

Interesting topic.In my units it's gas but it's common for my area except the dryer is electric.I have some tenants that love electric and others love gas and hate electric.It will be based on their past individual experiences dealing with utility companies on how they feel one way or another and what they grew up using.So I just go with what's common for the area.I do agree with low income tenants that have wild fluctuations in income that they will try some risky things to get by sometimes.Higher income tenants do not tend to think of doing such things as much is my experience.

Don't know if these are clerical errors or rent price fluctuation.

We fluctuate very slowly compared to many markets in America.

The market will fluctuate on you, so be sure your numbers work at the lower end. 

The notable exception is if you buy at the top of the market and need to sell at the bottom, but that is why you need a "margin of safety" in the form of excess equity created by a "killer deal" to insulate you from the short term market fluctuations.

IMO, fluctuating rents for the same unit sends a BAD message.

Prices can fluctuate block by block.

Their jobs change all the time, income fluctuates, credit is often trashed, even if you obtain a judgment they are uncollectible due to being under federal poverty guidelines for garnishment and for bank levy their funds are usually untouchable being social security, disability money, etc.