Most people would start off with a poll about pricing and such. Then you can get to know yout general art price range. Or as some other people do, creating a commission auction. Those dont give the exact general amount, though. After that, open an art shop and see what people like and such. That could be actual commissions, or you can sell ych slots.
As for the art program, there is a forum topic full of art ptograms and information about them. ^^
https://wolfplaygame.com/forums.php?f=35&t=10523
Note: I find that Medibang is a really good art program, but it can take a while to understand it. It took me around 3 months to find out how everything worked, but it was worth it in the end! I started off with Autodesk Sketchbook (which by the way is completely free if I remember correctly), went over to the SAI trial, and slowly switched to Medibang in the end. c:
Fall Month: 2 
Night 
Clear Moon: 
