Does it cost to develop an app?

Hi!

I'm pretty new to app development coding, but am interested in trying it out!

I have a background of coding languages in C, C++ and Python and would say Im an amateur in coding in general. But I have heard that Java is pretty common to use in Android apps and therefore I will give it a try or learning Java is the first step in my plan.

My question is, does it cost to develop an app? Since I am doing this for fun Im not looking for extra expenses really. If it does cost, what parts of the process costs money if Im thinking of programming it myself and upload it in Google Play?