The market practice now, as stated in the Realtors Guide and endorsed by the Realtors Body, is that for rentals below S$2500.00 a month, the tenant pays half the month's rent as commission to the agent. But this should be made clear and agreed upon before viewing takes place.
To pay one month's commission is probably too much; not to pay is probably not right. Like in every business, there will be agents who are prepared to make exceptions - sometimes half a loaf is better than none. But generally, we feel it is fair renumeration, and one gets what one pays for. 
