It's a lot of hassle mate, if you're trying to balance it with a full time job as well you find you never have enough time to do enough to keep it going and the amount of people you get messing you about is unreal (ask any of the traders on here and I'm sure they'll tell you that). I tried it when I was a bit younger but you get to a point where it's just not worth the effort. And with cars as cheap as they are now from dealers I don't think people are buying much 'privately' unless they're something very specialist like Cossies or extremely cheap. And then of course if you're dealing in stuff like Cossies even if you're experienced it's still possible to get stung and lose a lot of money.
Just trying to be realistic and give you both sides of the coin mate.