ime is generally the most influential factor in the rent vs. buy decision. Unless you live in an area where property prices are rocketing upward, it generally does not make sense to buy a house if you can't commit to owning it for at least 4 years.

Transaction costs
There are a myriad of fees and charges and deposits required in buying and selling a home. These transaction fees can cost you 10% or more of the selling price of the home.

With costs like that, it generally makes sense to stay put for a while and wait for the property's appreciation to cover your transaction expense.

Be conservative
If you are not sure how long you will own a house, make a conservative guess. The average American moves every 10 to 13 years.

Most people move for lifestyle changes, not financial reasons. You may get transferred, read a compelling article about the joys of life in rural South Carolina, or decide that you and your spouse shouldn't be living in the same city, much less the same house.

In these cases, the last thing you want is to stay because of money, but for the rest of us, it can make the difference between making a profit and taking a loss on housing.