We can easily determine the additional cost of electricity, gas, water usage, and consumables (paper towels, laundry detergent, cleaning products, etc.). 

If it's grease I've had good luck using either the drain cleaner someone else listed earlier or dishwasher detergent with hot water, let set overnight- it's the strongest detergent you can buy, but won't damage plastic pipes (can work on slow toilets as well, since it breaks down, er "food").

Consumables like detergent, toilet paper, paper towels, coffee (if you offer it) and on and on.

Buy a small box of TSP detergent powder from Home Depot.

The "house contribution" goes to all communally used items such as trash bags, dish soap, toilet paper, laundry detergent, coffee, etc. 

Also have it in the lease what items they are required to get on there own (example: Tooth paste, Toilet Paper, Paper Towels, Laundry Detergent, Light Bulbs etc.).4.

yep in your house. so in the summer time AC bills will increase and the house will smell like TIDE detergent while the dryer is on. if you have the units in a closet or area with a closed door all that moisture can cause mold as well. sorry, you really should vent it!

or would you recommend removing the popcorn and cleaning with TSP detergent?

For the oil staind I use Dawn dishwashing detergent straight and let it soak for a few days and then hose it off .

The tenant said in court that she had thought it was because her daughter had drank some laundry detergent.