The challenge in events and sports mainly in the need of succeeding in an event you have no much control. Can't miss the golden moment. The experience and skills comes in to play more in those cases. Other than that the effort you have to made to produce the final result is comparatively low in events and sports if event is not a wedding.

With real estate and architecture you have room to trial and you can take time to produce something extraordinary with your expertise. Stay home mums will not succeed in any of those cases unless client does not have a good eye or ready accept anything for the low money they pay.