500 normally for maid room
there are 2 type of agent, landlord agent and tenant agent,
if u engage them, means they r tenant agent , will help u find room, but u need to pay them commission
if u saw some advertisement that rooms are available from some agent, most prob they r landlord agent, means they will get commision from the owner if they are able to sublet the room out, this you no need to pay commission to them, coz the houseowner will pay them, they are not allowed to get 2 commission at same time
however, most of the time, the landlord and tenant agent will work together, landlord agent will contact another tenant agent, so that the tenant agent will get commission from potential tenant.
no free lunch in this world

Actually, I get the contact from the PropertyGuru. So, I think they are supposedly landlord agent. Furthermore, the rental is also same with the advertisement they posed. So, I wonder they may only wish to entertain me whenever I reach Singapore. What else can I do ?