Since buying a home is all in the numbers, you’ll be dealing with a lot of math. If your math skills aren’t the best, that’s okay. You can always use a pocket calculator or even the one in your smartphone. Knowing what to expect is more important than how you calculate the numbers.

The most important numbers you’ll encounter are the 1) down payment, 2) closing costs, and 3) ratio of monthly housing costs to your monthly gross income. There are many other costs involved in purchasing a new home but most will be included in the closing costs. Closing costs include appraisal fees, mortgage points, the realtor’s fee, mortgage application fee, and more fees, fees, and fees that may or may not apply in all cases.

The down payment is probably the most important number you’ll have to worry about. Without the required down payment, the purchase of your dream home will never happen. Many banks and seasoned realtors still go by the 20% rule. If a house costs $200,00, you’ll be required to put up a minimum down payment of 20% or $40,000. During the house shopping phase, you might run across developers who self-finance the houses they’ve built. It’s not uncommon for developers who offer their own financing to accept minimum down payments closer to 10%.

You can also use your down payment in reverse to determine how much you can afford to pay for a house. If you have $10,000 and the minimum down payment is 20%, then divide $10,000 by 20% or $10,000/.20. With a $10,000 down payment, the maximum you could afford to pay for a house would be $50,000. However, you might get lucky and find a developer who offers his or her own financing and requires only a 10% down payment. In that case, your $10,000 divided by 10% would be $10,000/.10 or $100,000. Under those circumstances, you could afford a $100,000 house.