You can only buy properties in Qatar in certain places in the country such as Lusail and The Pearl. There are others as well but you would need to check. To buy a property I would recommend you go through a real state agency. Home Dealers is a very good one and they will walk you trough the entire process and tell you all the steps you need to follow. The documents will depend on how are you planning to pay for the property (cash or mortgage). But an agency will do all the paperwork for you including lawyers, registration, and to get your titled deed etc... I wouldn't recommend you buying a property without an agent.