The wonderful folk at Blizzard have now allowed the creation of Death Knights on any realm, so long as you have a character somewhere that is at least level 55. Apart from DK's being a fun class to play, this opens up a host of ways to make money on a new realm.
Each time I've completed the DK starter zone, I have had a starter fund of about 25g. Its not much, but its a lot better than the handful of silver a level 5 character would have when reaching the big city for the first time. It is more than enough to start searching the auction house for bargains.
Death knights start the game with no trade skills except first aid. The old standby gathering professions mining, skinning and herbalism will need to be levelled up from scratch, but it is insanely easy to farm the newbie areas on your epic mount. Even the low level materials can fetch a decent sum on the auction house. Dual gathering works well as always.
The one massive advantage that a newly minted DK has over any other starter class is of course that it is high level and well equipped at the start. They make brilliant farming characters, easily able to run through any lower level instance. Unholy spec seems to be the easiest here, with better AOE abilities. Blood spec makes a decent alternative that is able to self-heal even when swarmed by half an instance's monsters. Frost spec is viable also but not quite as good as the other two in a farming role.
At level 58 or so, probably the best instance for farming would be Scarlet Monastary. Lots of silk cloth, reasonable quantities of green items and heaps of vendor gray make this definately worth your time. Shadowfang keep is another smallish instance that is worth farming, particularly if you have skinning as a profession. Lots of the BOE blues in SFK are valuable for sale to twinks.
The instances inside Orgrimmar and Stormwind, Ragefire Chasm and The Stockades respectively, are worth considering. RFC is much better in this regard, dropping a large ammount of linen cloth and loads of low level greens. Stocks drops linen and wool cloth in decent ammounts but has a very poor rate of green drops. The main reason for quickly farming either of these instances is their proximity to the vendors and auction house!
Death Knights are a boon to anyone starting fresh on a new realm even if the DK itself is not your primary character. I almost miss starting things "the hard way".