At $800 that listing is most likely fake, or otherwise is just for one room in a unit.
Ads on this site can actually be pretty good (I found my place right now on here), but it's important to ensure they're legit. One way is to look at the picture quality--too nice and it might be generic publicity photos from the estate, and not photos of the actual unit. Other places to look are ., 99.co, and Carousell.
Hidden costs: if you're renting just a room, usually the listed price covers internet and utilities already. Otherwise, if you're renting a whole unit, you'll be paying internet and utilities (plus connection fees when you move in), and probably aircon servicing and repairs, but those can be negotiated.
Another hidden cost for renting, regardless of room or whole unit, is stamp duty, which is 0.4% of the rent for the contract period, which you have to pay on lease signing. And of course there's the deposit, which is usually one month rent for one year.
As everyone else said, you can only rent "normal" units if you have a long term pass. Otherwise, you'll have to go with
Serviced Apartments, which are more expensive.