Definition of opponent for English Language Learners. : a person, group, etc., that is against something (such as an action, law, or system) : someone or something that does not want something to exist, be done, etc.
Generally, your first mortgage payment is due on the 1st day of the 2nd month following your closing date. For example, if you close in February, your first mortgage payment will be due on Aproil 1st. Generally speaking of course.
Mortgages traditionally quote and charge interest on the basis of repayments in advance which means if you take out your mortgage on day 1 then the first repayment is also due on day 1 (the alternative would be repayments in arrears whereby the first repayment would be due after 1 month).