Before we get into anything, I just have to ask... are you a photographer or an actor? Or both? If you are planning on taking your own headshots and don't have a ton of money to invest in a camera, please take a look at this link, as we have an entire video that shows how you can do your own headshots easily with a camera phone. Then you can have them digitally edited with us so they have a blurred out background and professional look.
Now, onto the article.
Selecting a camera is almost as difficult as having a baby. On second thought, I'm kidding. It's easy! I highly recommend either Nikon or Canon, because they are both great brands, are versatile, and will have clients believing you are a true professional. Just remember that you can't switch from one brand to the other because the lenses aren't interchangeable.
The basic pros and cons: As of this writing, Canon is typically ahead of Nikon in video capabilities, along with having slightly cheaper lenses. On the other hand, Nikon has faster auto-focus and generally sharper lenses. I personally own and recommend Nikon equipment, as it seems to be easier to use too.
Once you've decided on a brand, choose a digital SLR camera that costs at least $500 to $750 for the body. It's best to buy a full-frame camera (normally around $1,800) but if you can't afford it, that's fine. You can always upgrade later. In my opinion, the most important aspect of the camera is that it has great pixel sensitivity, meaning it can take pictures in low-light situations and the shot won't be too grainy. You need something that can shoot at a high ISO because headshots demand fast shutter speeds so your subject doesn't get blurred out as they move.
Along with checking the ISO/low light sensitivity of the camera, also be sure to look up the number of megapixels the camera shoots at. I recommend at least 12 megapixels. Just remember that higher megapixel cameras don't always offer better quality, so don't let that be your only deciding factor. Having too many megapixels can also wind up taking up a lot of space on your computer if you shoot in a RAW format. For headshots, you really don’t need too many megapixels. That’s more for landscape photography.
IMPORTANT!!! Don't forget, you'll also need to buy a headshot lens. Shooting with the wrong lens won't leave you with good results.
Read about lenses for headshots here.
If you're interested in learning how to shoot awesome headshots for people and want to know how to direct them into great expressions (not to mention learn lots more of the technical side of headshots), check out "Shoot Headshots That Pop!" an awesome eBook written specifically for people wanting to get into headshot photography.