1. High-end full frame DSLRs is good, but it costs more ($1500 or more).
For most real estate photos, crop frame and P&S digital cameras with
wide angle and zoom lens for shooting interior and external photos will
be enough.
2. Interior may be low light situations. Therefore, you may look for
a a fast f2.8 lens and/or build-in flash.
3. Small camera that you can carry it around easily.
Here are some my recommendations.
Canon EOS Rebel T1i / 500D
15.1 megapixels
18-55mm (28.8-88mm equiv.) 3x optical zoom and Max. Aperture
F3.5 with IS Kit Lens
Accepts optional external flash units
Optical Viewfinder
DSLR with interchangeable lens
HD Video
Sony RX100 III Advanced Camera
20.1 MP (effective) 1.0 inch Exmor R® CMOS sensor
BIONZ X™ engine for superb detail and noise reduction
ZEISS® Vario-Sonnar® T* 24-70 mm lens with F1.8-2.8 aperture
Built-in OLED Tru-Finder electronic viewfinder (EVF)
180º - tiltable LCD for selfies
Sensor Type1.0 in type (13.2 mm x 8.8 mm) Exmor R® CMOS
sensorNumber of Pixels (Effective)20.1MPOptical Zoom2.9xISO
Sensitivity (Still Image)(Recommended Exposure Index)ISO
125-25600
Nikon D5000
12.3 megapixels
18-55mm (27-82.5mm equiv.) 3x optical zoom and Max. Aperture
F3.5 with VR Kit Lens
Accepts optional external flash units
Optical Viewfinder
DSLR with interchangeable lens
Vari-angle LCD
HD Video
127 x 104 x 80 mm /
5.0 x 4.1 x 3.1 in.
Approx. 560 g (1 lb. 4 oz.) without battery, memory card, or
body cap
Olympus E-620
12.3 megapixels
14-42mm (21-63mm equiv.) 3x optical zoom and Max. Aperture F3.5
with Kit Lens
Accepts optional external flash units
Optical Viewfinder
DSLR with interchangeable lens
Swivel LCD
130 x 94.0 x 60 mm /
5.11 x 3.70 x 2.36 in.
Approx. 475g / 1.04 lbs without battery, memory card, or body
cap
Panasonic Lumix DMC-GH1
12.1 megapixels
14-140mm (28-280mm equiv.) 10x optical zoom and Max. Aperture
F4.0 with Kit Lens
Accepts optional external flash units
Optical Viewfinder
DSLR with interchangeable lens
Free-angle LCD
HD Video