It’s fine to buy things with a balance transfer credit card for as long as it offers 0% interest on purchases. But if your card does not offer 0% on purchases, or this introductory rate has ended, making purchases could prove very expensive.
Whenever you carry a credit card balance from month to month, there is no grace period for new charges. That means finance charges begin to apply as soon as you swipe your card. A 0% purchase APR protects you from this temporarily. But if you don’t pay off what you spend by the time regular rates take effect, interest charges will quickly eat away at your savings.