If you're a renter, you've probably heard you're throwing away money each month. Homeownership has been sold as the American dream, and in some cases it's a great decision. If you're thinking of taking the plunge, make sure you consider the financial facts. Personal finance expert Lauren Lyons Cole runs you through the essentials to consider when making a decision. First, she says, look at the rent ratio: take the list price of the home you're considering buying, and divide it by the annual rent for similar properties. If the number is 15 or less, then buying is cheaper than renting. You also need to look at your savings, your credit score, and the time horizon of how long you expect to stay in the house.