Hi Joseph,
the question about earning money is really complicated and there's no sure answer since it warries a lot for each and every artist. It really depends on what kind of art would you like to do. Then you can look-up some artist, who have already succeeded in your chosen direction and see their stuff. From that knowledge you can get a basic idea of a "level" you need to achieve if you want to be a pro basically. Then there comes the most important part and that is whether you are good at "selling yourself".
However if we are not talking about doing full time artist, but just getting some side money, it's in my opinion a lot easier since it depends on your contacts. For example I am not that good and I am already able to make some little money time to time becouse I am getting exposure amongst my friends and that means that in case they need something they know who they can go to and after you've done a thing for one friend and you've done it well enough then ofc he/she is going to recommend you to his/her friends and so on.
As I've already searched a lot about it in order to find out my art possibilities I can recommend you one thing. Just focus on doing what you love and do it a lot and after some time and a lot of effort when it comes to getting exposure the "paid stuff" may eventually come to you.
I think this video (Becoming a Professional Artist) that Marc did explains it pretty well. You can always also search for opinions of other artist because there's a lot about that topic on the internet, but you will find out pretty much the same stories. 
As for the Photoshop sketching it really just takes practice.. I think it took a while for everyone to get the right feeling with tablet, especially when you don't have an expensive one.
Anyway welcome to the forums!
Hope this helps and see you areound.
