it does not ruin your credit. if you would like to build up your credit you could apply for a secured card which means you give them x amount of dollars and they give you a credit card and if your account is in good standing after a year they will upgrade your credit status and refund your money. they ask for the money b/c u have no credit and they need to protect themselves. your credit score is determined bu how much money is available to you (credit) to how much money you owe (debt) for example if i have 10 credit cards and each one has a line of credit for 1,000 i have 10,000 available but if i owe 1,000 then the percentage is 10% debt to credit so your credit score would not be effected but if i owe 7,000 on the same 10,000 thats 70% and your credit score will drop. also paying late and skipping months lowers your score. debt is not only on cc also car lease home mortgage etc… hope this was useful