...All about to change though, January 1st!! Government just issued the new Income Tax Law. No details as yet, but there have always been income taxes on renting property here, 10% if earning up to $133,000 a year, so maybe it'll be something like that, which is what Hong Kong charges. If it's any higher, they probably won't get any expats coming here, and all those here will resign!

http://www.arabianbusiness.com/573800-qatar-income-tax-to-be-imposed-in-jan