Nowadays learning to play the piano is easy, you don’t even need a piano (acoustic or digital). All you need is a MIDI keyboard and a computer (which you already have). A MIDI keyboard is also called MIDI controller, it does not make sounds, but it does record the key sequences and dynamics. You can get one 61 keys for less than $200. Then you don’t have to worry about buying a piano and if it doesn’t workout, what to do with the piano.
You will need a software for your piano, it’s called Synthesia (which is a video game). It’s a free download and will get you started. After you install the software just hook up the keyboard with the computer with an USB cable.
All you have to do is watch the falling vertical bars, when a bar hits a key you play that key. There is no hurry, it will wait for you. This is a lot of fun and you will learn to play songs quickly.
The free version allows you to play a number of songs, if you want to play all the songs and free play you will need to upgrade to the full version for $29 (2015).
If you don’t want to play games and want to learn piano properly – here is a good alternative