Switching to coin washing machine and dryer

I’m the landlord for a duplex in San Diego, CA. The electric washer and dryer are on separate water and electricity in a detached garage. I’m looking for ways to cover the expense of the water and electricity and I’m looking at “coin” operated washing machine. Being a Millennial I hate coins and cash, and I don’t want to have to visit the units twice monthly to remove the coins from the washer dryer. A) are there any recommendations on buying vs renting pay per use machines? B) if buying what is the best type/brand Thanks!