Mike, I think Sergio is right; the most important question is not what gear but what pictures you’re going to sell. And that requires a few customers. Your equipment has to earn its keep. Different types of photography will have different revenue ratios for equipment. There is also the computer, printer and other equipment which will also have an earning ratio. Then you’ll need to have maintenance contracts because the client is not going to be tolerant of your technical problems. It will all need to be upgraded in 2 or 3 years.
There are several routes to take to be a pro; apprentice – yes leaving collage is just the beginning of your education, equipment is optional. Join a co-op or partnership, maybe an option. Go it alone, if you do, don’t do your own printing, find a good printer. I have yet to meet a photographer that can print color as well as a professional printer, and only a few that can print mono as well (I’ve met a lot of photographers). You get another advantage, the less time you spend printing the more time you spend behind the camera, you earn more as a photographer. And you need to earn 4 or 5 times what you think is a good paycheck, so to take home $100,000 you will need revenues of $500,000. The extra covers sales and marketing 15-20%, equipment maybe 30-40% and the rest is split between materials, T&E, admin and your pay at maybe 20%!
Where was the equipment to begin with? Buy a camera that will last you 10 years, simple light that you can put great lenses on. Take it with you on every assignment, use it too so it becomes part of you it will save your life several times over. What should it be? The best kit for your type of photography you can buy and only use half your equipment budget. Used gear is fine, take a trusted friend and research the market before you buy. For the clients work hire the kit you need and charge it in the expenses – I do all the time.
Your business will need to create customers of your photography, your equipment needs will be driven by the customers. Unless you want to be a webmaster that also takes the occasional photograph!
Finally write a business plan, and work to it. All you asked was what camera to buy!