Ragefire Chasm is one of the first dungeons you will encounter in WoW, the mobs here are around level 15 so you can start solo farming this zone pretty early. If you are level 70+ this zone can be done in about 5 minutes.
If you are low-mid level (30-50) you should take it a bit slow in here, but if you are over level 70 or so you can just run in and pull the entire zone then start looting. You will be making the most money from equipment and linen cloth. One run provided about 4 stacks of linen that sells for about 15g on my server. I can do a run in 5 minutes so thats 60g in 5 minutes just from the linen meaning 700g in an hour just from the linen. The linen along with other cloths sell really fast as well so you don’t have to wait for the money to come in like you do with the gear you will be selling.
From one run i got:
4 stacks of linen = 60g
1 BOE Blue = 50g
10 BOE Greens = 100-200g
Misc. Gems and Disenchants : 10g
Total : Atleast 200g from 5 minutes of work.