Hey, I learned to play exclusively on synths and organs! Didn't really touch a real piano until I was in my teens (even though my dad is a piano tuner/technician). Of course, I didn't take lessons, either.
That said, you can usually get a piano either cheap or for free. Before taking it home, however, it's always a good idea to have a technician come and look at it. It could just need a tuning, or it could have cracks in the soundboard, need all the felts replaced, strings replaced, action repairs, etc. Always good to know what you're getting into before-hand. But if you have the space, a real piano is the way to go.