Quote: "What is necessary for making an RPG?"
patience and time
if your not commited then an RPG is well out of your reach, online or offline doesn't matter which.
my advice would be find your favourite RPG, Zelda - Final Fantasy - Grandia - etc... then base yours on a proven working system.
Try to get most of the elements working similar, then you can work out the specifics as you go.
most important thing is you need a STORY, you can expand it later but you need a background story (aka why everyone is in crazy clothes battling space aliens from jupiter or whatever) and then a game story which the characters will follow
making the bg story helps continutity and scripting the specifics of the main story.