The "Basic Income"
Not all players take pleasure in crafting. It can be tedious, time consuming, and the gear you produce can be replaced with drops in many cases at the same level. Hours can be spent running back and forth from auction house, to bank, to forge, to auction house, to forge, to bank, to Wowhead, back to auction house, and so on. If that doesn't appeal to you, the "Basic Income" might be perfect.
The problem many crafters run into is an age-old problem of "independent merchants and distributors" everywhere. In many cases, the stuff you can sell for the most profit is also the stuff you need to consume to make things. In many cases, professionals in WoW have to decide between leveling their profession and being able to afford pet food. One way to avoid that conundrum is to take two gathering professions. That way everything you gather, you can sell without consuming it, and you won't be worried about using up your ore to make armor or using up your herbs to make potions. You won't be able to make either!
"Basic Income" continued.
Taking two gathering professions means you just gather up what you find along your path, and then dump it in the auction house when you get a full stack of it. Many times, professionals will rake through the auction house looking for reagents, rather than farming them on their own. A leatherworker who is level 70 and has just started Leatherworking will probably be glad to buy stack after stack of low level leather, rather than riding their epic mount around Mulgore skinning cougars and wolves for a day and a half. So, you can play on the tendency of crafters to farm the auction house before they farm the wilderness, and make a lot of money from it.
I usually recommend Skinning be one of your gathering professions, if you go this route. You'll be killing a lot of beasts anyway, and it isn't like you'll need to track the corpse after you just made it. The leather you peel off your kills might not bring you piles of gold as you first start out, but there's almost always a leatherworker looking for a bushel of leather. The higher your targets' level, the better the leather you'll pull off them. Leatherworkers themselves can combine lower level leathers into higher, as well, so don't be discouraged if all you get is ruined scraps. They're not really ruined! Sell 'em to Joe Dragonscaler.
Mining is another good one to take. There is a high demand for ore at practically any given time. Mining is the only gathering profession whose resources are in demand by more than one crafting profession. What's more, that ore is in demand by three: Blacksmithing, Engineering, and Jewelcrafting all use the metal and stones obtained through mining. Whether to smelt or not is kind of a local decision, depending on the market. I have always had better luck selling unrefined ore than selling bars. Remember that Jewelcrafters are able to prospect raw ore rather than smelt it, sometimes getting precious stones out of it. If you smelt your ore before putting it on market, you'll lose the customer base of prospecting jewelcrafters, which can be quite lucrative.
As far as taking two gathering professions goes, my suggestion is always for mining and skinning, for the reasons I list above. Herbalism can certainly be a profitable venture, but it's not one with which I have much experience. I tend to feel mining has a little more draw than herbalism, because more crafters have a demand for ore. On the other hand, everyone has a demand for potions, so herbalism is certainly a good option.
The advantage to this system is clear. You're gathering things for free, and won't necessarily be spending a lot of time doing it. Then you sell them, and the only cost to you is the auction house posting fee. The money you make incidentally from this method will probably get you a mount as soon as you hit forty, with enough to spare to train and buy yourself a whole new set of Mail armor, to boot. In addition, if you ever decide to take a crafting profession, you'll already have a pair of gathering professions to choose from. You could gather up to level 40, get your mount, and then start saving the resources you gather rather than selling them, and be set for a full profession's training in no time.
One Option: Engineering
There's a reason so many of the screenshots I post are of gun using hunters wearing goggles! I've always enjoyed the advantages offered by Engineering, and found them to fit well with a Hunter's usual playstyle. I'm a Gnomish Engineer, and always have been. Please don't take my lack of testimony about Goblin Engineering to be a criticism. I just feel Hunters have sufficient ways to deal damage at range, and therefore never went that route. Here are a few of the devices I've found most useful in Engineering.
Gnomish Death Ray: This device is made and only by Gnomish Engineers and is bind on pickup. Unlike most Engineering devices, the Death Ray does not actually require that you be an Engineer to use it. Many people report a dramatic drop in efficacy when it is used by a non Engineer, though. This device charges up by doing damage to you, then fires a bolt of energy which can hit for over 2000 in one shot. This is problematic in melee, where you are already taking damage from your foe. Often invoking the ~100 DPS to yourself for those few seconds can kill you in that case. But a Hunter is usually not taking damage. You can afford the charge time while your pet tanks. The Death Ray is a great little addition to your arsenal at the levels when you'll be able to make it, but beware. The damage dealt does not scale up past level 60. By the time you're running around Outland, taking six seconds out to deal a couple thousand damage is a terrible idea. You'll be frequently getting close to that much from just autoshots, many of you.
Goblin Jumper Cables XL: These are made only by Goblin Engineers but are usable by either Gnomish or Goblin. They are an upgrade from the normal jumper cables, with a little better chance of success. These can save a whole group in the hands of a Hunter. When it looks as though the party's doomed (the healer and tank are both dead, for instance), you simply feign death. Once the fight is over and all your foes have run back to where they started, you come back and jumper cable the healer. They don't work every time, but they are practically essential for any Engineering hunter.
Gnomish Net-O-Matic Net Projector: Made by Gnomish Engineers and usable by either Gnomish or Goblin, the net-o-matic nets a target in place for 10 seconds. This is my "don't leave home without it" trinket for beast handling. When you tame a beast as a Hunter, the beast takes it as a hostile act and charges you. You cannot heal or run or counterattack without breaking the taming channel. So what you do is, you lay a freezing trap between you and the beast to tame. Then you shoot it with the net gun, which again holds it in place for 10 seconds. You net it and begin taming. In 10 seconds it breaks free and charges you, hitting your freezing trap. You keep taming. By the time it's out of the freezing trap, it's your pet. The net gun's use is, I confess, highly risky. You might possibly experience varying results in use. That, however, is part of the debatable appeal of Engineering.
Gnomish Poultryizer: The endgame of Engineering can be boiled down to one question, between Gnomish and Goblin. "Would you rather shoot a rocket at someone, or turn them into a chicken?" In many ways, it is a question of philosophy more than mathematics. As I mentioned above, hunters already have some reasonably reliable means of dealing damage at range. On the other hand, we only have one way to silence spellcasters (interrupting them is helpful but not the same). The Poultryizer is a ranged silence with a 15 second duration. It allows your target free movement, though they cannot cast spells or use ranged weapons. With a caster, this is a great way to trap them. A ranged caster who cannot cast will run at its target to engage in melee, regardless of whether there's a freezing trap in the way.
That is just a few of the specific devices available to a Hunter Engineer. There are more in Engineering, and certainly as good reasons to take other professions if you do decide to craft. Taking two gathering professions is not the most exciting career to embark upon, but it is a reliable one. Consider what you want for your character, and where you want to take it? Then consider how much it'll cost to get there. For the casual hunter, there's not a lot of ways to make solid gold reliably before you have a mount.
Clearing the Chamber
These are only a few suggestions. I always think it's best to pursue a career field in which you're interested, rather than one which is mathematically or monetarily superior. A profession which you love doing which makes you poor (ahem) will ultimately be more fun in the long run than a profession which you hate which makes you gold. You may be an elven huntress whose love for the forest demands she be an herbalist/alchemist, or a dwarven hunter whose family tradition demands he be a blacksmith/miner. Try what you feel like, and do what you like.