WOW!
I started loving & growing plants at a very young age, but I think I was older than 4y.o.!
(In fact, I don't even remember being four years old, so I really can't say for sure!)
I always had an interest & appreciation for plants, animals, bugs & nature of various forms, but it's too far in the past to remember my exact age. Was always there as far as I know.
More specifically, like others, I was fortunate enough to work for a nursery at a very young age. (I started around 14-15 y.o. thru unusual circumstances, 1st hanging out & then working at a small nursery/plant shop... first buy doing grunt work & learning all I could. Worked there part time & weekends until my early twenties, eventually assistant managing. Best experience at that time of of my life.) My interest began seriously with Cp's (around 11 or 12) and my learning expanded to other plants & things as the years passed.
I don't know your situation, as one size doesn't fit all, but at this point you may want to consider raising plants yourself & selling them to local plant shops or other small shops. Even places that aren't plant stores will buy flowers, plants & CP's.
That alone will give you a feel for what it takes to do this for a living, and if you are good at it & have some luck, (persistent, disciplined & committed) you could get things going earlier than you may think. It really doesn't take a lot to get started, doing something you love. You don't have to sit around waiting at this point. You could be doing it (on a small scale) even now!
If you aren't, what are you waiting for?
(While we can always find excuses for what stops us from doing something, the person who really wants to do something, does it! They DON'T sit around wishing, they don't just focus on the on problems & let them turn into excuses. They see problems, but then find ways DO what they are wanting! You don't have to plan out every aspect of this before you begin.
Go! DO! Now!
I think the only reason I posted this was to see if anyone knew any good areas.
From what I see, the "Best Area" to do it, is where-ever YOU are!
It is not about some "right", special place to do it in, that will guarantee good results.
It is ALL about YOU!
Good luck!