based on your budget and...
This will be a paid job. Budget is approximately 100 USD per image
your quality expectation...
mage size is A5 (210x148mm – 8.26×5.82 inches)
Color, muted tones. Water color style
Mature/western looking characters
Story setting is in a medieval fantasy world with your typical magic, runes, and castles
Sample images of the style, quality, and level of detail that I'm looking for - https://drive.google.com/open?id=1zIku62mMOBAaEeBxXhbqPwq3n50L1gUU33
you should really up the budget. I made some calculations, and assuming the artist works 5 hours for 1 page, then ($100 / 5hrs) the artists gets $20 dollars an hour for this gig. That's low in general, but perhaps ok for some (those who are desperate for cash). You even expect the comic to be coloured with some medieval fantasy detailing, which I believe is asking for too much.
I hope any artist who sees your ad will consider this, and for you to change the budget or at least lower your quality expections. I'm freelancer on the side so I'd know what to expect, and I wouldn't want any artist to be compensated/treated like this. Unless they need the cash, in which case be my guest. So I really hope @imdurian consider some changes.