Mr T the building trade in general has a pretty bad name whereby one of the first concerns going through a customers head is 'How do I not get ripped off and how do I know they will do a good job?"
Now you're going to argue you will only take on 'small' jobs and you're not trying to 'rip someone off', That might be your intention now but you've already stated that you're going down this route because you want to provide for your family, which is all very admirable until the need to provide for your family is so great that you do take on that job which is beyond you capabilities, you might just pull it off, you also might just mess it up and end up ripping that customer off inadvertantly, even more so when you don't have the financial resource to hold your hands up and pay someone else to do it including the replacement of materials.
You've spent a long time on the forum so i'm sure you'll notice just how many jobs get undertaken by people that are well out of their comfort zone, you'll also notice the misery it causes.
Ok say you do manage to reel yourself in and refuse to undertake anything but the simpilest of jobs. Your answer is that you'll tell the customer 'I'm really busy so can't do it' in order to save face and not ruin your 'reputation'. All well and good, but i'm afraid when talking through the job with the customer they will either realise you don't know how to do it because you can't answer their questions... or you'll make the answer up. This is damaging to the industry and trade in general as it makes customers even more distrusting of the next guy to walk through the door, or worse they get their judgement questioned when the customer says 'The last guy didn't tell me that and he said you can just do x"
Nobody is trying to stop you from earning a living, they are trying to protect their trade which is littered with far too many people undertaking jobs they have no idea how to do.
You're fairly young and just like everyone of the guys on here who were once your age, maybe just a little too self confident. I bet if you ask, almost all on here would say they hit a certain age, looked back on their younger self and thought "damn I was cocky sod and maybe I didn't know as much as I thought I did and maybe wasn't so good as I thought I was"
But you won't agree with that and you'll think you're different... I know because that's exactly what everyone else thought when they were your age. It's just life.