I shoot some architectural photography for a couple of architects. To do it very well (and I'm not saying I do) is technically challenging. For architects you are trying to emphasise the features they consider important.So, if space is a feature you use a wide angle etc.
For estate agents (I have had several discussions with a few friends who are agents) there are different requirements. The problem they all raised is that there is no cash in the pot for better photography on the typical sale and to break into the higher end of the the market is very difficult. They also have a problem with potentially misrepresenting the property and the use of very wide angle lenses is an issue as it can make a room look far larger than it in fact is.
When selling my own property I did do my own photography but used a 50mm lens in portrait orientation with a panoramic head (for the interior shots) and stitched the images to get the wider angle whilst still maintaining a representative perspective and size for the room.
You will notice that many info sheets for properties use a couple of exterior views and for the interior views tend to frame and focus on features. This avoids the problem of trying to get the whole room in a single shot and possibly misrepresenting the size of the room. Use a 12mm lens in the average UK lounge and you can make it look the size of a town hall committee room.
A lot of estate agency photographs are very poor but unless you can show that better images will result in more sales they will stick with what they have got. I was also warned that estate agencies can be very slow payers and will probably only pay if/when a property actually sells. The kind of money they were talking about for photographing a property would not cover the cost of doing it once you took into account travel costs, equipment costs, insurance, processing time etc. When I looked at it, after costs, I would be working for less than the minimum wage and in some cases it would actually cost me money to do.
Don't let me put you off though

If you can find a way of getting them to pay a reasonable rate and pay it when you photograph the property (not if/when they sell it) then you might be able to make a go of it.
John