I have a good friend who is a RE agent and started shooting listings for him last year. It took me about 8-10 shoots to get comfortable and settle in on a method.
Lots of time can be saved in post by taking a little longer on leveling the camera and getting the lighting right whether ambient or flash. My niche is houses in the $250K-$850K range in the greater Seattle area. Most of my jobs entail an hour of drive time or less (round trip) 60-90 minutes at the location and another 60-90 minutes post processing with PhotoShop CC. My fees range $150-$200 in most cases with additional charges for excess travel time, particularly large houses, virtual staging, and high angle shots.
I am now working with 6-8 agents pretty regularly, having done 30 listings so far this year. I post each shoot as an album on Flickr and also provide a link to Dropbox for a zip file of the photos, one set 2400x1800 resolution. Usually 15-25 shots per property and while I promise next day delivery, in most cases I deliver the edited shots the same day.
Pricing seems to vary widely by market and while agents can certainly be tight, if you work with good agents they realize their time is better spent doing things that make them money and paying you for freeing up their time makes sense. Frequently I will shoot a seller's house while the agent is finishing the listing paperwork/contract etc.
I started with my 6D and 16-35mm F4L along with a Samyang 14mm. Recently have switched to my 7D2 and Sigma 8-16mm. I have 3 Yongnuo 600RT flashes, rarely need to use all three but regularly use one off camera and occasionally need a second. Time is money - I can shoot everything with the Sigma lense and am not spending time swapping lenses like I did with the 6D. The 14mm Samyang needed barrel distortion corrected in every shot. Sigma doesn't suffer from distortion so less editing time in post.
Many will merge or layer multiple ambient light shots so as not to bother with flash. I find that by balancing ambient and flash 95% of the time I can get the shot with a single capture, again saving time in post.
I am keeping pretty good records, and seem to be grossing in the $47/hr range. Not getting rich, but it is reimbursing me for all the gear I've bought over the years and making it easier to get approval for more as the need/want arises. Doing much more business than I ever expected to, so much in fact that I went "legit" and run it as a Schedule C sole proprietorship side business.