if your only earning minimum wage realistically getting a car between 6000-10000 is more reasonable beings there is maintenance and insurance... and other things to pay for in life.
Divide the cost of the car (plus tax, fees, registration, etc) by the average take-home amount you get weekly, minus any other expenses you have. This will give you the number of weeks it will take you to save that amount.
Well, since you more than likely wouldn't pay the entire amount up front for the car, it really depends on your loan.
You would make monthly payments to your bank, so it really depends on what you and your financial assistant at the bank agree on.