'Personal' broking being is not legal in Qatar, a is any form of work without being part of a legal entity. That said, many people are doing it, and frankly it's giving real estate a VERY bad name. The government are supposed to be introducing regulations in the new year, but I'll believe it when I see it. These regulations will
theoretically only allow registered real estate companies and individuals to do business. How they plan to enforce this, I have no idea.
To setup legally, you will have to form an LLC, though this is a costly exercise. Qatar is still not embracing small businesses for expats.