If you live in a house for less than 2 years, you will be paying taxes for the profit on the house you sold, unless, you are getting a house comparable to the previous house (this is a tax loophole).

If you live in a house for more than 2 years, gains on the sale are tax free for the first $250,000 if you are single and $500,000 if you are married.  If gains exceed these limits, than the difference will be taxable income.