Location is the biggest contributing factor when deciding your pricing structure.
We are based in the South and have a minimum charge of £10 irrespective of what is required. We then price according to time taken and work the cost out at £25 per hour per operative.
But please think about your location, If I went up north and tried to dictate such prices I would be sent packing with my tail firmly between my legs. The best way forward is to do some market research in your area, ask around, friends, family etc and see what they pay, this way you will start to get a feel for what is and isn't reasonable. Then depending on when you see yourself slotting into this pricing structure market yourself accordingly.
Hope this helps,
Regards,
Trevor