How wide of an angle lens do I need?

A wide angle lens is very important when taking photos indoors, as we have to do in this business. So what's all the talk about 35mm equivalent? And why should I care? First, most manufacturers will specify the lens in a 35mm equivalent form as well as the actual mm of the lens. An example would be: 5.4mm-16.2mm (28-84mm 35mm equivalent) or 18mm-55mm (28-80mm 35mm equivalent). Using the 35mm equivalent measurements gives us something to compare with from camera to camera. On digital cameras, since the sensor size varies from camera to camera, the mm measurements differ from camera to camera. So to make it easier to compare, they give us measurements in 35mm equivalents, or what it would look like in a standard 35mm film camera. So in the example above, the 18mm-55mm Canon Kit lens on the Digital Rebel is as if I was shooting a 28mm-80mm lens on a 35mm camera.
Now, how wide is wide enough? I will recommend people get 24mm on the wide side. How you get to 24mm is up to you. If you buy a camera that has a 24mm lens, great. If you buy a camera that has a 35mm lens, and add a 0.7x adapter, you'll get some distortion, but it'll still get you to 24mm.
Right now, many manufacturers seem to have been moving away from the 24mm compact digital cameras. I'm not sure why, because almost every real estate agent would want one, as well as many people that take landscape/travel photos. There are only a couple out there, and if you take away the Kodak ones, that leaves next to none. If you know of any, let me know and I'll update my list.
So can I still get a compact digital camera and use it for indoor shots? Yes. Go with the 28mm route, and get a 0.85x adapter.
Or, for the next step up, consider the Canon or Nikon DSLR cameras. Pick a lens such as the Sigma 10-20 (16-32mm in 35mm equiv) and get the Canon Digital Rebel XT or XTI, or Nikon D40 or D50. These are the entry level digital SLR cameras and will be more than adequate for almost everybody.

Now, here's what photos look like at different mm ratings. All of the specs are given in 35mm equivalent. The room is a living room that is 21 feet by 11 feet. I was standing in the farthest corner shooting across the room. The camera was mounted on a tripod, and set to a manual exposure of 1/10 of a second at iso-100. Since I forgot to match the aperture across the photos, I manually adjusted them all to f/3.5, the same as the initial 2 photos.

20mm:

This is the living room of a particular house shown taken with a 20mm effective lens (18mm *1.6 crop factor * 0.7x adapter) Note that you can see the lamp on the left side, as well as wall space in front of the lamp… all the way to a piece of artwork on the right side. The corners are dark due to the combination of the 18mm with the wide angle adapter of 0.7x. This wouldn't be the case if I had a "real" wide-angle lens (which I do not have yet). Also note that there is some barrel distortion that is noted as curvature in the passageway to the hallway.

24mm:

Now take a look at 24mm. Note that the lamp is just starting to get cut off, and the framed art is ½ missing. (This was also taken with the 18mm * 1.6x * 0.7x but taken zoomed in just a tad.) Still get a good sense that the room is longer than it is wide.

28mm:

Here is where we start to lose more of the room. The lamp is almost completely gone, and the framed art is not there. We still get an ok idea of the room, but not of the original size of the room.

34mm:

This photo, taken at 34mm, has no sense of the room size anymore. It could be a 11x11 or it could be 21x11. No one would ever know. This is not a good photo to use because it just doesn't depict the room well. Compare it to the first photo which shows so much more of the room, or even the 24mm photo. Do your sellers a favor and get a wider lens.

There are only 3 point and shoot cameras that have 24mm wide angle lenses, the Kodak P880, and the Kodak V570, and Kodak V705, of which I don't like any of these 3 cameras. The quality is poor compared to every other camera I've seen or used.

Bottom line is this: you may want to consider an inexpensive Digital SLR camera such as the Canon Digital Rebel XT or the Nikon D40. They both are about $500, and you can add a 10-20 type lens such as the Sigma 10-20 for about $500. Total investment would be about $1000. If you decide to buy online, be sure to purchase from reputable vendors such as http://www.bhphoto.com , http://www.jr.com , http://www.adorama.com , http://www.amazon.com , or you could check other vendor ratings at http://www.resellerratings.com before you purchase.

Cameras with 28mm or wider:
Canon SD870is, Powershot S80, Powershot Pro1
Fuji Finepix F480 Zoom, E500 Zoom, ix E510 Zoom
Fuji Finepix S9000Z, S6000 fd, S8000 fd, S9100, IS-1
Minolta DiMage 7, 7i, 7Hi, A1, A2, A200
Leica Digilux 2, D-Lux 2, D-Lux 3, C-Lux 1
Nikon Coolpix P50, Coolpix 5400
Olympus FE-200, FE-290, C-5060 Zoom, C-8080 Wide Zoom, C7070 Wide Zoom, SP-550 UZ, SP-560 UZ
Panasonic Lumix DMC-LC1, FX07, FX50, FX01, FX30, FX33, FX55, FX100, LX1, LX2,TZ2, TZ3, FZ18
Ricoh Caplio 500G, RX, R1V, R2, R3, R30, R4, R5, R6, R7, R40, GX8, GR Digital, GR Digital II
Samsung Digimax A55W, L74 Wide, Pro815
Sony DSC-F828

Cameras with 24mm or wider:
Kodak P880, V570, V705 (23mm)
Nikon Coolpix 8400 (24mm- not availble anymore)
Ricoh Caplio GX100 (24mm)
Sony DSC-R1 (24mm) (if you're going to spend $1100 on this camera, why not get a Canon XTi and 10-20 lens for $1000?)

Out of 820 digital cameras, only 6 have 24mm wide angle lenses!