The Credit Geeks have built a number of calculators to help you calculate the cost of borrowing. The idea is that you can both budget for that debt, and also see the difference that tiny increases in interest rate will make to how much you eventually pay back. Go on, give it a try!
First try a mortgage with 6% APR and then with 7% APR. Then a loan with 8.5% and 11%. Then get your head around the cost of loading up a credit card with a 20% APR, and see how crazy credit card debt is. Our aim here is to help you make smart choices about whether you need debt, and if so, how much. Your credit score will affect the APR you are offered, so plays a crucial role in how much you pay to borrow.