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.
You'll have to write a check for the amount at closing. When you make your first mortgage payment, that payment will include interest for the 30 days immediately preceding the due date -- from the day first of the previous month. The cash you pay at closing covers the interest up until this point.