WTC Question About Self Employment

I work 10 hours at the moment, I used to work longer hours but had to do less hours at work due to rehabilitation from a car crash.

Now I'm back to my old self- work cannot give me any hours; I just wondered, if I started my own business, just repairing PC's nothing major, could I claim WTCs? As in work 10 hours and make the six hours up on self employment?

Do I have to earn over a certain amount? Or could I work for less than the minimum wage?

Just wondering really, thanks.