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it does depend on how often you would need it as I would be spending time on it outside of work and coding my own games too :)
I would say to commission characters, I would charge £5 per character with an idle animation and negotiable for anything else. I would do one revision with this if required. They would come in this characters size (I think it was 20 or so pixels? And would include each frame as png and a piskel file (in case they're layered).