All landlords ask for a security deposit to ensure that the apartment will be yours. If you move in your deposit goes towards any damages if you break lease & suddenly disappear. Most people use the security deposit towards their last month rent before they move out which in the eyes of 98% of the landlords of NY is unprofessional. What some landlords do is they ask for a small deposit upfront if there currently showing the place This small deposit is to hold the landlord for the days hes not showing the place in case you come back 3days later & say I decided im not going to take the place.
If you do decide to take the place you just have to pay the difference.
But don't forget at the end when you decide to move out you get your security deposit back.... more