Save your money a bit longer.
For 75% of your shootin being real-estate, moving to full frame and getting wide stuff, etc, it's going to cost you a ton and result in some web-images. You gain next to nothing. You'd be better off buying lighting if that really is your bulk work, and a good lens with minimal distortion (not ultrawide). On APS-C, that would be 16~35. There happens to be a very good lens for that by Canon... This would be better than getting a full frame just to produce web-images for real estate. Not trying to be negative, just trying to figure out the allure to full frame for this purpose.
Unless you feel the other 25% of what you shoot warrants the move to full frame. It's not a magic bullet, you need good lenses to really make this worth while, which means primes, or very expensive zooms.
Personally I would wait a bit longer. Let the holidays pass. Let the next release cycle land. Then get a 6D later, when prices have dropped even more. By then a 5D2 may even be $700ish too. The next release cycle will have a lot of full frames hitting the used market. That's the better time to buy, gain from those who are chasing gear cycle upgrades.