how to find a short-term (2-3 months) apartment?

Hi everyone

I am coming to Spain to study Spanish for 2-3 months (from September onwards). I have checked websites looking for rent of apartment but what i can find is all about holiday apartment which is very expensive. I am wondering where i can find real non-holiday type of apartment for rent? also whats the normal price for the monthly rent in Madrid and Barcelona?

Thanks for your help in advance.

Tiantian