If you don't want uncertainty hanging over your head, this is probably the wrong business to try and get into. Not saying it's a bad industry, but job security for someone just starting out is generally low. As far as time is required, since you already have a degree you can just put your nose to the grindstone and pound out your ratings as quick as you can get them. From there you should start looking for a way to build your time up and then start applying to the companies you want to work for. It can take as little or as much time as you want; it all kind of depends on your motivation, study habits, ability, financial backing, etc.