Just to emphasize the incorrect answer below, so that you (and anyone else from NJ reading this) are very clear as to what is and isn't legal in NJ.:
"But the sky's the limit on how much of the total rent payments on the lease your landlord wants up front."
NO, NO, and NO...... not so in New Jersey!
NJ Landlords can only LEGALLY collect a maximum of 1.5 month's rent upfront (in advance) including security.