Hello, this is my first post and I want to share with you an easy and fun way to make gold. I'll write this post from my DK experience (this may also work with hunters/pallys/warriors but I'm not sure).
Back in wotlk, I was completely broken and my only source of gold came from gathering professions (insanely boring imo). Before starting to use jc/ench as my main gold professions, I started to solo magtheridon and doomwalker, that meant 500g + BoE items every week.
In cata, raegwynn solo'd TK, what meant a lot of money everyweek (unless you were farming the mount). I've sold like 20 runs, 5k per normal run and 10k if the mount dropped, that's alot of money for 1 hour of effort every week. But that's part of the "good ol' times" now, becouse almost everyone can solo TK now.
Let's talk about the present, about MoP, what are the most profitable runs?
Well, [Raiding With Leashes] is the best friend of run sellers atm. Yes, pallys, warriors, hunters can solo it easly, but it's a tedious job for mages, priests, rogues, "add the class you want here". Fortunately, it's piece of cake for DK's.
Transmog runs are another good deal, you can solo TBC and ICC raids, and if you know the bosses mechanics it's pretty fast (excepting hard modes).
Note: always ask to the buyer if you can keep the recipes and patterns, some of them are really expensive, especially the sunwell patterns and the buyer generally only goes for the transmog gear. For more info check Raid Recipes - Supplemental Snatch List
Black Temple (warglaives)
Warriors and DK's can solo it, so your only buyers will be rogues. Full clear 2 hour max.
Sunwell (legendary bow) except kalecgos and maybe brutallus, the rest should be easy.
For wotlk you will need more gear so I'll update this when I get enough info about the mace and shadowmourne.
To conclude I'll like to recommend you to loot EVERYTHING (Patterns will add a lot of gold to your wallet in case you're lucky) and watch raegwynn/mionelol videos for hard encounters.
I hope you enjoyed this guide and if you want to add something let me know.