I need to know all the details. So you tell me what you need, I ask a bunch of questions, and then I send you an estimate. If you agree, we proceed. In most cases, you’ll be presented with some rough ideas, which may or may not look rough. We talk again; you tell me your thoughts, I tell you mine, we agree on a direction. Maybe a couple directions. This can repeat, not too many times, until we get to a final draft. You approve it, and I’ll create final files.
Almost always, you will be billed at the end, for the same amount estimated; I work on trust. If the scope of the work increases, I'll let you know that the cost will also increase. If the work gets stopped, chances are you’ll simply be billed for the amount done so far, or for a “kill-fee” of half the amount quoted originally.
How long does this all take? Of course, it depends. We would need to talk about it!