Is it impossible to rent a decent house in Rotterdam??

I am a Master's student in Rotterdam.
I have been looking for a house in Rotterdam (Netherlands) every day for the past few weeks. It really seems that it is IMPOSSIBLE to find a house IF YOU DON"T have a job contract!! BUT how can I work since I study here full-time? I have looked in every internet resource (in English and in Dutch),classifieds,and makellaars!!
I am looking for an appartment in Rotterdam (n-o-t in Zuid) at about 40m2, for about 650 euros. Am I asking for too much??
I really have a problem cause the only houses I found required a job contract!!
Any suggestions?

Thank you in advance

In reply to everyone that answered till now, actually I found a lot of houses for up to 650 But they all needed contract! And a friend of mine rented a nice 40m2 appartment for 320 Euros inclusive!! So, how can you say that 650 are not enough??

I do not find it very odd for a broker to be asking for some kind of guarantee when it is about these amounts of money. You are right when you say most of the brokers will ask for a job contract. However, most of the brokers will also accept you as their tenant when your parents would be willing to be your guarantor (they have to sign).
To answer your question regarding you asking for too much: I think it should be possible to rent an apartment for 650 euro's in Rotterdam, but it is not going to be the most luxurious. I take it you study at Erasmus University, so the most convenient would probably be to rent a place in Kralingen. However, I doubt you will find anything there in this price range. Since you are not willing to rent in Zuid (understandable if you ask me, although I live there myself), I would advice you to look in Noord (Blijdorp). There are some nice affordable apartments there and the neighbourhood is actually quite good.
I have not really looked into it, but a couple of minutes Google brought me to http://www.wonenmvm.nl/, they have an apartment in the Borgesiusstraat for 650 euro's and an apartment in de Witte de Withstraat for 675 euro's (ex gas and light), both at nice locations.
Keep in mind most mediators will charge you one month of rent for their services. However, most of them work in a no cure no pay fashion.
Let me know if you need any help in translating or in anything else!

Rotterdam sucks....
no chance, too many reasons not to get a flat.

You are looking in one of the most popular parts of one of the most popular towns in the Netherlands.

You either have to pay much more, have been on a waiting list for the social housing for many years or start looking farther outside the city center, maybe even a few towns away.
650 euro is the price for a room in some parts of town, not for a whole apartment.
Even with a job contract you will have difficulties finding a house or apartment for that money.
Students do not have a good reputation with property owners.

Did you not try the student housing office? They'll help you get something .... but probably not an apartment as, well, you're a STUDENT ....

650 Euro a month? In Rotterdam? That's for a room, dear. Not an apartment.