Follows my usual ToS:
http://notreallydaily.com/commissions/
Samples of styles also available on page.

OB: $75 - Lined Sketch or Speedpaint or lower
$120 - Cel Shaded or lower
$150 - Soft Cel Shade or lower
$175 - Digital Painting or lower
$300 - Clothed/Nude variant (2 versions of picture)
$500 - Additional variant to client's choice

Yes:
Any sex and/or gender
Any species including humans
Adding clothes (only get one version unless $300 goal is reached)
Changing expression
Changing body proportions (i.e: chest size, genitals, chub, missing limb)

Conditional:
Wings for extra (+%20 of price) unless AB
Extra limbs for extra (i.e: second pair of arm) depending on complexity

No:
Changing pose
Extreme body proportions changes (i.e: non-humanoid body shapes such as taur, naga, mermaid, etc...)
Extreme extra limbs (i.e: head, torso, lower body, etc...)