Are you a student, going to study in Singapore? It means you must find a convenient locality and find an affordable flat. There are endless options, but it is not easy to get one at the first sight for long term stay. If so get ready for short term rentals to accommodate.
The foremost point is to know how much money you wish to pay as upfront. The deposits as security are omnipresent in each rental contract and this is applicable in Singapore as well. The amount mostly is a deposit amount for one month. In fact, some may demand in advance a 6-month deposit as security.