Many families are now purchasing digital pianos to learn on. And why not? They're relatively inexpensive, take up very little space, and produce high quality grand piano sound. But there are certain drawbacks to owning one. For example, it's a good idea to play an acoustic instrument before trying a digital one. Why? Because no matter how well the piano sound is sampled, it will never match the pure acoustic sound and richness of a "live" piano. This factor is very important to some because they want to experience that organic sensibility only a true acoustic can give them.
Because you have to start from where you are. This should be fairly easy; Otherwise you have not started from where you are. A suggestion is to start writing piano pieces for beginners in a progressive order. The idea is that as the pieces get more complicated for the player they will also become more complicated for you to notate and compose and you will subsequently learn as you write.