The absolute cheapest you can get away with is a Canon 350D or a Nikon D50. And whichever you get, you’ll need 2 of them. (As a pro, you need a backup for every piece of essential gear. No matter what item malfunctions, you have to keep on shooting!) One step up, and you can get the Canon 30D in combination with a Canon 350D backup, or a Nikon D70/ D200 in combination with a D50/ D70 backup body. If money is no object, get 2 Canon 1DsMk2’s or 2 Nikon D2X’s. For the lenses, you’ll want a 70-200mm zoom for candids, something like a 17-55mm zoom as your workhorse, plus maybe a few f/1.4 or f/1.8 primes. Some photographers like to also throw in a fish eye lens. (Again, double up on ranges you can’t do without.) Add 2 flash units, a ton of batteries, a tripod, plenty of memory cards, a hefty carrying bag, software (Photoshop with some plugins and perhaps Capture One), and a few other odds and ends, and your set.
Your looking at a total price of, ummm… $3000 for a budget setup and $7000+ for anything decent.