If you shoot images for HDR, you will need to take bracketed shots with the exposure changing each time. Why multiple exposures are needed is further detailed in the What is HDR photography? article.
Usually each exposure is separated by between 1 and 2 EV steps.
Many cameras support an AEB (Automatic Exposure Bracketing) mode which will automatically take the shots for you, with the right exposure for each one.
Here is a list of features you should look for in a camera, to make it easy to use for HDR photography.
You should aim to use a camera that has AEB mode, and allows EV step increments from 1/3 to at least 1 EV.
Having up to 2 EV step increments is better. This is especially the case if you are shooting real estate, as the range of contrast in a room with a view on the outside can be very large.
A camera that allows no more than EV step increment will require almost double the same number of exposures than a camera that allows 2 EV to cover the same range.
Ideally, the camera should be able to take at least 5 auto-bracketed shots.
The minimum number you need will depend on the EV step increment. The smaller the maximum increment, the more shots you will need.
3 shots at a spacing of 2 EV covers the same range as 5 shots at 1 EV, and 5 shots at a spacing of 2 EV covers the same range as 5 shots at 1 EV.
If your camera supports only up to 1 step increments with a maximum of 3 shots, this generally won't be enough for HDR photography.
If your camera doesn't have AEB at all, you can change exposures manually to get the bracketed shots you need. You may also need to manually change the exposures when your camera doesn't support the EV range required for a particularly high contrast scene.
However this is cumbersome and slow, and you will generally require a tripod.
Some cameras have additional software that can be loaded onto them, such as CHDK and Magic Lantern for Canon cameras, which allow a greater number of shots to be taken in AEB mode. These are free, created by independent developers, but don't support all cameras.
It's helpful if the camera allows more than the old historic 30 second exposures.
If you use AEB in dark places, 30 seconds may be too short (think of the longest of 9 exposures at 2EV steps). If you are limited in exposure length, you may need to increase the ISO to compensate for this.
When you're using long shutter speeds, even small camera movements during the capture of the photo can give you blurry images.
Cameras with a mirror often shake more, because the mirror moves during the capture of the shot.
If you shoot with a long lens (e.g. 200mm), you may see the effects of this, even if your camera is on a tripod. With wider angle lenses the effect may not be so obvious, but you may still get a lower qualify image from the movement.
Here are some ways to avoid camera shake:
Note: You should be able to use mirror lockup, live view and AEB all at the same time. Some cameras allow AEB and mirror lookup only as alternatives.
Check the video below has more information on getting crisp photos and avoiding camera shake.
If the light is good and you're using short shutter speeds, it's often possible to shoot AEB shots handheld. If you do this, you can make use of the image stabilization of the camera or the lens to reduce shake.
The faster you can shoot the bracketed photos, the less movement occurs in the scene while you are taking the shots.
A camera with a fast frame rate is especially helpful capturing scenes where there are slow moving objects. It may be possible to take the photos so close together that the movement is not noticeable in the final result.
The only possible downside of fast frame rates is that in some cameras they may introduce more shake.
Note that not all cameras use their maximum frame rate when taking AEB exposures.
When taking bracketed shots, it's ideal if the camera uses auto focus for the first shot, then uses those settings for all the rest, without focussing again. This speeds up AEB operation, and keeps the focus the same for all the shots.
If your camera does auto focus for each shot, using manual focus should speed things up.
Generally, you won't need any extra equipment than you would to take single photographs. For a DSLR or mirrorless camera, this will of course include lenses, which will vary depending on what kind of photos you are taking.
For landscapes, a wide angle zoom lens such as 16-35mm or 24-70mm, and a medium telephoto such as 70-200mm should work well. For interior photos, the most important thng is to get a wide angle lens such as 12-24mm.
A tripod is also good to have, especially if you are taking photos inside in low light, or night shots.
For more information about equipment needed for real estate photography, see this article.