My advice would be to just get out there and do it and try not to let some of the replies that are sure to come in this post deter you from doing what you want in life. Just be aware of the pay cut you’re surely to experience from your current job. But if you can live simply then do what you want. I’m not an instructor but I’ve done my far share of forum reading and most of the time, it can be discouraging. I just think most of those people would rather live a little more comfortably then live off a scuba instructor pay, which I can’t blame them: it’s not for everyone. But do what you want man, I’m on my way to do the same. Not sure if this is the advice you were actually looking for, but just wanted you to take everyone’s advice with a grain of salt.