Taxation is very low compared to other taxation in Belgium: http://www.globalpropertyguide.com/Europe/Belgium/Tax-Pages
Round trip transaction cost is sky high though. My experience is that the 21.10% estimated here is a gross underestimate: http://www.globalpropertyguide.com/Europe/Belgium/roundtrip-...
Does Belgium have no property tax? That's the only way such low rents could work.