Hey Wayne,
Just thought I'd chip in my [2cents]. I was lucky enough that my first client was a guy who setup his own business and he was extraordinarily helpful with helping me with this exact question. I would love to start my own business "Chris' Carpentry"

but I doubt that would happen.
Anyway my point is that I charge about R50 an hour and this is dirt cheap it however affords me roughly R500-700 per job as profit. That includes, wear, petrol and metrial costs. I am happy with that, still living under my parents roof but I doubt that would let me live happily. I'm sure you, being a professional, could easily charge R200-300 per hour. Labour is always the most expensive part of build, in just about any job.
Just my 2 cents. Maybe call around to competitors and ask them how much they charge per hour, get a feel of where the market is at?