Thanks for your replies!
I understand that but thing is: I want to invest to it and buy some specialized courses as well, not only diagnostics equipment for over £4k and make it a waste, plus the manufacturer is giving their clients technical training.
I'm thinking about buying it and starting as mobile or weekend/evening only diagnostician and then grow to fully working garage in a few years. I like getting my hands dirty while fixing my car and I'm quite good at it, I just don't have any recognizable education for garages to hire me.. And also I would like to do it more often and, in time, get some profit out of it.. If you know what I mean. I don't want to keep working for someone all my life.. And I have abilities that I'm not using now..