When you're thinking about buying your first home, it might seem like it's all about the down payment. You save for years to have it, and you base a good portion of your home-buying budget on it. Next comes the mortgage. How much will you owe each month in principal, interest, taxes, and insurance? How does that compare with how much you currently pay as a renter? If you've figured out how to tackle those two huge expenses, you might think you have it made in the shade. With