I'm not a realtor, and I agree with Marda about consulting a professional in your area. I'm on the south east coast, and the idea of unstained concrete floors brings to mind a house still under construction. Not something I would want to move into. Maybe it is different in your area, though. I'm not cutting edge, I'm sure.
But I can tell you this: "I" would never buy a $200,000 home that had unstained concrete floors, unless there was a reason they were that way (the home was un-finished and I expected to spend another large some of money finishing it; or the home was finished except the flooring had not been installed yet, so as to be determined by the buyer, etc.)
But a lived in home that the finished floor WAS unstained concrete? Nope.
My parents had not fully finished the basement of their home when they moved in. But they did stain the concrete floors. Now, they have hard wood on them. It was a work in progress, but they never put furniture down before there was something on the concrete.