Michelle Lipton has a great post discussing what you might want to take into consideration if you decide you really, really do want to be a screenwriter. Or, alternatively, if you already know in your bones that you are a writer, and you think maybe script writing is for you, then you really should read what she has to say. IMO. (click on her name above)
There are plenty of other screenwriters out there posting on the net that you might want to familiarise yourself with too - check out the links, over on the right.
The key concept is SELF EMPLOYED. Which is likely to go hand in hand with full time, or part-time, work as an employee in a day job that pays for the roof over your head and the food on your table. Because writing takes a long time to bear fruit - Terry Pratchett told me he couldn't give up the day job until he'd published his 6th book. In the event he waited until he had 7 books out, to be safe. (I quizzed him briefly at a book signing several years back as he kindly put his signature on my latest prized purchase.)
Even Phillip Barron has a day job, ask him, go-on. He may kill me. LOL.