Don't listen to the people who say you should not sell your services, for as long as you make sure that what you sell is indeed a service.
Advertise in the LFG channel that you have pre-raid BIS and that you will pass on any loot [even if it's an upgrade]. Also go for 40g/80g/etc. because thats quite easy to split.
Remember everyone that basic farming can net you up to 400 gold per hour and this service only 80 gold if the group is quick. you are not getting rich, just covering your basic needs.
It should be self-evident that you don't charge anything if you wish to loot as well, or for heroics.