Not to be the bearer of bad news, but IMHO, the first thing you should know is that a lot of people, all over the world, know Photoshop extremely well and will work for peanuts (or even for no pay), so you will encounter an astounding amount of competition in trying to become a professional freelancer.
You will need to know more than Ps to step into the world of freelancing. You will need to be strong in Illustrator and After Effects. Most clients like vector files and animation. I am speaking from experience here.