Adding Fees to a lease Providence Rhode Island

[Akeim Fin]

TLDR: How do I charge for washer dryer hookup giving myself max flexibility? 

I have a gorgeous 3bd 1 bath that I have been struggling to fill. Currently there is no laundry and no pets. I am considering adding a washer dryer hookup in the basement. Can I charge them to use the washer dryer space? I don't want to put it in the  lease. I want something that I can easily stop if something goes wrong like they decide to wash their entire family cloths and the water bill goes $$$$. This is an owner occupied space so I want a low risk, hight flexibility option. Can I call it a fee and add it to their rent monthly. Seems like a silly questions but sometimes calling something a fee vs rent can have an impact if you have to go to court.