having just switched back to skinning (from alchemy) I can say honestly, that skinning and herbalism are the initial money makers. A stack of 20 liferoot can go for 2g and that's for a lowerlevel herb. A stack of stranglekelp can easily go for like 10g. That stuff is SERIOUSLY hard to get alot of, not to mention it's used in alot of potions. The upside to both of these is that herbalism requires no added costs, skinning only like 60 copper for a knife. Everything else when it comes to leveling your skills you have to spend money on added items.
If you don't take Skinning or Herbalism, I strongly suggest tailoring. Skinning and Tailoring are MADE for hunters or anyone that do alot of solo grinding. Since if you grind beasts you get leather and if you grind humans you get woool/silk/linen/mageweave/runecloth pretty much everything you kill can help you. Not to mention when you have tailoring, once you can make 8 slot bags, you start bringing in money. Everyone needs bags. EVERYONE. So once you hit silk and can make silk back packs (12 slot bags) that's like 1 or 2 gold a shot. If you have an alt it's even better. But either way, it's nice because not only do you get the cloth off humans but you get XP and money. It's like it pays you twice. Plus with Tailoring you need light leather for a few patterns but that is easy and cheap to get and if you have skinning you are covered.
with Engineering, Mining, Smithing, leatherworking you need so many other things it gets rough and expensive.
My 2 copper on the topic...