Where you are aiming is a dead-end I'm afraid

It fails the 2 golden rules for making any kind of money in this world:
1) There's not much demand for it - so very few companies (about 0 big companies in the world!) do it. Just about no-one, in the country, wants to use this 'overclocking' and 'slotting in a few cards' service you offer.
2) Lots and lots of people can do it, especially kids that are prepared to work for minimum wage. You're not remotely specialist you'll be 'common' therefore easy to replace. SO as a life-rule you're going to have to compete with all and sundry for every single penny you earn .. which will keep your wages very low for the whole of your life, until overclocking/fitting graphics cards becomes impossible or unnecessary in 14 years (or whatever) at which point your TOTALLY unskilled for ANYTHING

In other words 'Dear KFC I am a man at the 'height of his career' with 3 kids to support, do you have any work oh god please?' .
Basically you're trying to do a job that is the same as someone saying 'I want to fit specifically Sony Blu ray players into people's TVs, deciding which HDMI slot to use etc and making sure the disc drawer opens correctly, and fit the unit into any TV cabinet they have'.
You see the problem? Who'd pay for that? What is the demand? It's easy!
(Call me harsh, but maybe in 20 years you'll look back and think 'Thank Christ I listened to the bloke off t'net'!!)
What to do? Learn C++ off your own back (its easy and off t'net you can learn it for free in 2 months to become good) then get a 'starter job' as a programmer somewhere on 20K - move up from there ... Long term being a decent programmer will give you a fairly average/happy middle class life forever. Nothing mental good, but nothing mental bad. A nice semi-detached in Suburbia, a nice family car, 2.4 kids and a dog, never really struggling to pay the bills or buy anything you really want with a bit of saving ..