Mining and skinning are both great ways to make money at low levels.
Disenchanting is a really easy way to make money once you already have a couple of gold seed money. Just buy up all the weapons and armour in the ah priced at 10s or less b/o and sell the dust/essences. Whilst its not uber-money compared to Outlands its easily going to be enough to get your ride with a bit left over for goodies.
The problem with using disenchanting to make money at low levels is that you will outpace it...
If you don't level it by doing enchants you soon find that you can no longer disenchant unless you run lowbie instances or bid on low item level items at the AH, and even then you're only looking at the lower level mats.
On a couple of my servers, a stack of Strange Dust will sell for about 3g50s. A few piles of linen (which are the only cloth selling cheaper than silk on these servers, at ~15s/stack) and you can tailor enough greens for a couple piles of Strange Dust, so there certainly is a profit to be made off of low level mats.
Then all of a sudden you're at a level where you can hit up SM Cath. The end-bosses are a guaranteed Small Radiant Shard, which is worth a pretty penny since all those twinks out there want their Fiery Weapon enchants. If you havn't been dumping money and mats into your enchanting to level it up, you won't be able to disenchant it.
So.. no big deal. You can get enchanting up high enough with Strange Dust and a few Magic Essences... But then what happens when you start hitting Outlands and the money invested starts multiplying for marginal gains? Eventually the cost starts levelling out and you can make a pretty penny on high level mats, but at this point your enchanting is high enough that you can make some cash through enchants as well.
The point of that whole rant? Other gathering (strictly gathering) professions aren't much of a money-sink. You hardly have to invest into them at all to see scaling returns from them. Disenchanting will make you money, but as you level you'll have to put some pretty large sums of money into it to keep it up to date.
As far as farming at low levels... I wouldn't waste time with it. I'll grab whatever I come across in my natural levelling process and never have a shortage of funds. I certainly wouldn't go out of my way to run circles around Ghostlands collecting copper and tin, or running the lowest level instances for the occasional 1.5x Strange Dust armors. You level so quickly that in a week's time, you'll be making more money selling the Greys off of quest-mobs that you've killed (Rock Elementals in the Badlands, for example) than you would have if you held back to farm. Add quest rewards and other sellables ontop of that and the difference is staggering.