Yes, of course it's possible to earn a living domaining. Many people on this forum and elsewhere do just that.
At the same time, at the other end of the revenue scale, I would guess there are probably several times as many people who are basically "setting fire to money on their front lawn" in the sense that they are registering and renewing hundreds or thousands of domains with no real idea of what's good, what's bad, what's worth something and what's worthless, but who are persisting at it out of a wholly misguided feeling they're going to "get rich quick" out of it. The sad thing is many of these people will leave domaining thousands of pounds poorer and thinking it was all a scam, whereas it was actually their own lack of knowledge that tripped them up...
The advice you've been given so far is solid. Don't rush to register names. If you're buying from other people, try and concentrate on a few good names with solid value rather than grabbing at everything. Focus on "generic" domains unless you have a huge budget, as you may be sitting on "brandables" for years or decades before they sell (and most likely they will never sell at all). Avoid the siren call of extensions other than .co.uk and .com if you're really trying to make a go of it. Yes, there may be some money to be made from .org.uk and other extensions, but you need to be EVEN MORE experienced in domaining to do so. If you're buying to develop, then DO IT. Don't stockpile names you won't get around to, but buy 1 and develop it, then buy 1 and develop it, etc.
And if anything in what I wrote sounds confusing or unfamiliar, then the bottom line is you're not yet ready to start investing, and you need to do a LOT more reading and learning first. Reading costs nothing. Registering junk, on the other hand, has an immediate financial impact, and might even damage your chances of buying decent stuff down the road because you've blown your budget.
Good luck with it!