The nagging feeling that buying is something you should do is one big reason that millennials choose to buy, says Bill Nelson, a certified financial planner and founder of Pacesetter Planning near Boston. We've also been told that buying is an investment, and renting is "just throwing money away."

Adding up the costs. Many experts recommend buying only if you expect to park yourself there for at least five to seven years. What if you like your city and current situation but also have no idea where life will take you in the next five to seven years? Sometimes, "the most you can say is 'I plan to stay in the same spot, knowing everything about my circumstances, career and family today,'" says Jeff Tucker, an economist at home-price site Zillow.com.