Guy hit my parked car and now wants to pay in cash installments.

I was advised to post this here.

Guy hit my parked car. The damage is about 3.5 to 4 K. He does not want to go to his insurance ( not sure if he has insurance). He wants to pay in cash installments over few months. I am located in Colorado.

So if I let the the guy pay in installments, how do I ensure i get completely paid for my damage ? Any alternative suggestions you might have will be welcome.

PM me is you want more details.