options other than coin machines for a small building

Hello,

I have  a building I just purchased with two 3 bedroom units and I'd like to offer a laundry room option, but the coin operated machines are really expensive. I don't want to invest that much and then the tenants don't use it or don't use it much. I was thinking about getting a stackable washer dryer (much cheaper option) but not sure how I might regulate it's use or how to charge. Any suggestions?