DeltAlum is right - every time you take out a loan, especially a car loan or mortgage, your income will be verified. If your income is too low, the bank will be concerned that you won't be able to make your payments (even if your payments are quite a bit smaller than your monthly take-home pay) so they either won't make the loan, will charge a higher interest rate because of the risk, or will ask for someone (such as your mother) to co-sign so they can recover their money from the co-signer if you default.
The good news is, if you make your loan payments on time, you'll improve your credit rating, which banks also consider when deciding whether to make a particular loan.
Hope all goes well with the new car.
