Can't answer that question without more information. Do you live in a major city, in the suburbs, or in a mostly rural/farm area? How old are you? Do you own the car or are you making payments on it? How much coverage does your state require for personal liability and property damage? Do you qualify for any discounts like multiple car discount, good driver discount, etc.? Do you live in a no-fault state like Michigan? All of these things will affect your monthly payment.
If you're under 30 years old, it's going to be VERY expensive to insure an Infiniti M45 sport because (a) it's an expensive car, which means it'll be expensive to fix if you get in an accident, and (b) people under age 30 who drive high-performance sports cars or luxury sedans tend to get in more accidents than people over age 30. If you finance the car you MUST have full coverage on the car, and that's a lot more expensive than liability and property damage coverage. And if you live in a no-fault state, insurance costs more overall than it does in other states.
The only way to get a realistic idea of what you'd have to pay is to talk to an insurance agent. To be on the safe side, however, be prepared to pay at least $300.00 a month for insurance.
