I need a bit of pricing assistance as I'm thinking of opening up commissions after I've finished my exams for the year. How much would you expect to pay for something like this:

Charcoal sketch kids

or

Charcoal sketch maori

I use acid free sketch paper and charcoal sticks, along with HB pencils and ink sometimes to highlight areas better. Any help would be greatly appreciated with pricing of these as I'm stumped as to what to charge.