The idea can be anything. Fan art of your fav anime/cartoon character.
Pokemon. Digimon. Porn and stuff. Fursona etc.
If you're interested please put me a note about the idea of yours. Details and pic.

Prices Traditional or digital:
1. Sketch 5€
2. Lined 8€
3. Flat color 10€
4. Shadows 15€
5. Background 25€

6. Chibi 3-6€
7. Bigger than A4 30-40€

Why they pay so much. It's because of the ProMarkers. One pen costs me about 3,50€.
The prices are the same for digital art.

Ps. That background is from internet.