If I may make the assumption that someday down the road you will want to play a "real" piano, then the answer is... depends on the keyboard. A keyboard would be fine -- provided that it has weighted keys and a reasonable approximation of the feel and action of a real piano. There are a lot of good keyboards available which do just that.But you should avoid a keyboard which does not feel and act like a real piano. There are a lot of them out there, too, and for what I take to be your objectives should be avoided like the plague (which does not make them bad in any way -- just not appropriate to learn to play the piano!).