I missed this thread, it was heated in parts, I think some people have a bad case of sun stroke. Mr T I will give you one piece of advice, and its this be patient. There is nothing worse than digging a hole for yourself by setting yourself up as a 'tradesman' when you have limited knowlege of that trade. Whilst I recognise you want to support your family and get off the benefits, you need to be 100% sure that you can deal with the majority of work that may come your way. There are very few people that are in a position to 'cherry pick' which work to take on or refuse. As someone else pointed out there is a steep learning curve to go through, and even after you have done that, there are always problems you need to be equipped to find solutions on the spot and there and then. The consequences of a job going wrong can be catastrophic, financially and reputation wise.
I think the point people are trying to make is not so much about the tax situation, its about the fact they feel you are not experienced enough to undertake work, and complete it to a high enough standard of workmanship. Accept this as advice and not as critcism, learn your trade, learn it well, and listen to those who have been doing it for a very long time. Practice makes perfect, but do not practice this trade at the expense of a paying member of the public, that is just wrong.
You are not equipped to do the job properly yet, without supervision, in time you will be. Dont run before you can walk, this is a trade where you learn something new every day, and if you want to be one of the best take advice in the way it was intended and not as anything else.
Pebbs