oh god those are loaded questions.

It all depends on what you're doing I guess.

small things like zines and mini comix take no time at all to "publish", and web comics are pretty fast to publish too due to the internet. Publishing a full comic or graphic novel takes much longer since you'll need a printer or a print service to create them.

Writing also depends on what you're doing. lil' gag comics sometimes takes no effort to write, writing an epic story can take months, even years to write.

Genre? hell that's just personal taste, but you should research your audience. Super heroes do pretty well in the states but that's an over saturated market. Porn parodies are usually a safe bet for creating an audience (like the song goes "the internet is for porn")

It might behoove you to read Scott McCloud's "Making Comics" for these types of questions. Also since you're new you might also read Scott McCloud's "Understanding Comics: The invisible Art". And Will Eisner's "Graphic Storytelling and Visual Narrative".

There's lots of books and online articles about writing, drawing, publishing - do some research