I am asked for a security deposit to rent an apartment. Is this normal?

Yes, the security deposit is always required when signing a lease. Its amount is equal to 1 month's rent excluding charges. It could be used when you leave the apartment, to pay for any late rent, charges, T.O.M. or to cover any repairs to be made at the time of the inventory of fixtures.

Otherwise, it will be returned to you within 30 days if your inventory of fixtures at the beginning of your stay is in accordance with the inventory of fixtures at the end of your stay.