Selling a home costs money.  If you are not sure how long you will stay in your new house, you may want to consider renting.  If you have to suddenly move the value of your home may not have appreciated enough to cover the costs of buying and selling.  

The length of time that it will take to cover those costs depends on various economic factors. Average appreciation tends to be around 5% per year. In this case, you should plan to stay in your home at least 3- 4 years to cover buying and selling costs.  However if you plan on staying in the same area the other homes will also have appreciated roughly the same amount.  The real estate market can be particularly volatile, however, and dramatic swings up and down are not uncommon.