I want to buy a car but make a measly amount of money (how can I buy one)?

I have a 2001 Ford Focus with a little over 170,000 miles on it. It's not really running that well. I will try to keep it up with oil changes, tune ups, etc. But if I sell it, how much trade in value will it have? How much will I need to get a cheap car? I only make under 400 dollars every two weeks because I have a part time job so I barely have any money.

All you are going to be able to buy is another car with just about the same mileage and almost the same age. Your trade in value will be close to zero. You will not be able to finance a car making so little as you are not allowed to spend more than 10% of what you earn on car payments. And few places will finance a car worth under $5000.

Just keep driving the Focus for now until it needs a major repair over $1000.

Sadly, you won't qualify for an auto loan with an $800 monthly salary.