You need the water lines (in and out) for the washer, and venting to the attic/roof for the dryer and a special upgraded electrical outlet for the dryer. We did this but it was part of a much bigger renovation so I don't know how much it would cost just for this job.

My parents have this. A regular washer/dryer behind folding doors. It is actually their main level powder room. Looks fine as long as the doors are closed.

To clarify, I don't want to remodel the bathroom. I would leave everything as it is but add the w/d and get whatever plumbing would be needed or ventilation for the dryer etc.

I have a bathroom on the bedroom level that is rarely used. I'm thinking about getting a stackable washer/dryer and using it as a laundry. I don't need it to look pretty, just to be functioning. How much would I be looking at (approx) to make this happen?