Real-Estate photography is a great market for learning new skills, and earning money to support your vision. The marketing is far simpler than the more artistic jobs, and it's easy to build up a portfolio.
The average client is looking for clean shots (preferably some depth to the image with almost no shadows) and for only a few creative images (maybe none at all). But before we dive into that, you will need a portfolio!
When it comes to balancing your flashes with the ambient light, there are some simple ideas and a few basic rules that will make the job MUCH easier. One thing that has always helped me, is to remember that the amount of light from your flash is controlled mostly by the aperture. This in turn, means that the amount of ambient light can be controlled by your shutter-speed and ISO settings.