A sketch is a quickly drawn, and rather rough rendering. However, it offers a quick and cheap conceptualization of a subject that may not have any other visual reference.
~Separate Styles:
Bust - $8
Full Body - $10
~Additional character: Free! After 1, a $2 fee is added
Sometimes all you need is a good look. a good ink makes a rough sketch much easier to view and understand. Also great for colorists who want to color their own pieces.
Depth is important to flesh out the details of a subject. At this level, you'll be able to add depth to your subject without having to go overboard with the details.
For those who want full exhibition to flaunt their characters and go the extra mile. Usually better if there needs to be a certain setting or mood, or with necessary lighting.
I typically draw references with 2 3/4 angle views. Different characters have different things that need to be detailed. Because of this, we can discuss what can be added to fully understand your character. Full color is not necessary, and if anything, harms a ref sheet.