A washer/dryer for each unit a good idea?

[Fareed Fityan]

I recently purchased a duplex which is now completely vacant. There is a water heater and  washer/dryer hookup for each unit. I purchased a washer & dryer for the bottom unit, hoping to relocate it to a common area in the near future. The problem is now I just moved into the top unit and looking to rent out the bottom unit very soon. This will leave me without a washer/dryer. I am planning on having the future tenants pay for their water (each unit has its own address) and utilities anyway, so is it worth getting another washer/dryer set instead of building the extra storage to house it in a common area?

Just for some background, I was hoping to remove a water heater from the top unit and connect the pipes to have just one water heater hooked up for both units, but financially it will be a lot more expensive than to just buy another washer/dryer set.

So my question is: what would be the advantage to having one shared water heater for both units with one communal washer/dryer, compared to keeping the water heaters separate with one w/d for each unit?

Thanks!