Can apt. landlord make acceptance of delinquent rent conditional?

Attempt to pay past due rent(beyond 3 day quit period but prior to notification of unlawful detainer action) was denied unless accompanied by additional $580 "legal fee" and following month's rent, which is not due for another week. These conditions were not stipulated in prior communication w/ landlord agents re: this situation. Past due rent, parking space rent, Water/sewer/trash charge and $75 late fee were offered as req'd. by lease agreement. I know landlord can refuse payment and evict. It seems that placing these added conditions is possibly punative/retaliatory in nature at least and more extortion of single mom in duress(late rent caused by bounced child support check on rent due date). Grateful for answers even if just affirming that landlord is justified.