Answer:
At 18 you are of legal age to be legally bound by contracts that you sign. If you have a good history of paying bills that are in your name (cellphone, credit card, etc.) than it is safe to say that your credit score is in good standing. Lenders will look at your credit score, your current debt, current income, and based on that information determine your interest rate. At that age you should be more concerned with how you can make the money you need vs. borrowing the money. Borrowing money is expensive and if it is an unsecured personal loan, meaning there is nothing that the lender can fall back on if you stop making your loan payments, the interest rates can be significantly higher than if you have some collateral such as a car, home, etc.